US 2110825 A
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Description (OCR text may contain errors)
D Too Jo RM g5.
mh H K March8, 1938.
/ INVENT OR.
* MTM@ BY l M ATTORNEY.
Patented Mar. 8. 1938 PACKED TOOL JOINT Merton T. Archer, Toledo, Ohio, assigner to 'llhe National Supply Company, Pittsburgh, Pa., a
corporation of Penna ylvania Application Maren i2, i935, serial No. 10,692
This invention relates generally to pipe joints and more particularly ,to packed pipe joints wherein a packing is employed to provide a seal between the members making up the joint to d direction.
This invention may be conveniently applied in joints for connecting consecutive lengths of drill pipe to form what is generally termed a drill string, the length of which frequently exceeds l four thousand feet. The lower end of the drill string is provided with a drill bit for drilling oil wells and the like and the drill string in reality constitutes the shank.
A pair of coupling elements are generally employed in connecting consecutive lengths of drill pipe to form a drill string. These elements, commonly termed tool joints, comprisecomplementary pin and box members having threaded portions arranged to be interengaged to form the joint. The other ends of these members are provided with threads for coupling them to their respective sections of drill pipe, I have chosen this form of connection to illustrate my invention.
In rotary drilling operations the cutting bit on 'the lower end of the drill string is suspended in a well and rotary motion is imparted to the drill string from suitable apparatus at the well head. This motion is transmitted through the string to the bit for drillingv the well. The drill pipe provides a continuous passage through which mud laden uid is delivered to the bit. The con-A tlnuous ow of this fluid keeps the bit clean, softens the formation and ushes the drilling from the well hole. The mud laden fluid being delivered through the pipe under high pressure is inclined to leak through the joint connections and in such cases where leaks occur, sand, carried in suspension' in the uid, produces a destructive abrasive action, thereby destroying the tool joints and reducing uid pressure at the bit.
There are also conditions occurring in well drilling operations wherein it is desired to supply a back pressure valve at the lower end of the drill string during the operation of lowering the string into a well lled with fluid, to gain advantage of the buoyancy resulting from the displacement of the uid by the hollow drill string.
This operation sets up an external pressure head wherein the fluid surrounding the drill string seeks to leak through the tool joint connections to the interior of the string,
The lrst object of this invention is to provide,
prevent leakage of fluids therethrough in either in combination with the conventional type ofv joint construction, a seal to resist the iiuid pressure in its tendency to leak through the joint connections in either direction.
I attain this object by the provision of an annular packing ring inwardly adjacent the threads Y of the male member which is arranged to be engaged by an outer portion of the female member.
The packing lies in an annular groove in the male member spaced from a transverse annular abutting shoulder. The end of the bore of the female member is provided with a bevelled surface which engages the packing ring. The packing ring is preferably made of circular cross section. 'I'hus the advancement of the female member into threaded engagement with the male member brings the beveled surface into contact with the packing on the male member. Further advancement causes the packing of circular cross section to be urged into the space between the groove and the transverse shoulder deforming the shape of the packing without subjecting it to appreciable pressure.
The end of the female member engages the transverse shoulder in its screwed home position and the packing lies between them in a deformed shape but in a space slightly larger in volume than it would ordinarily ll if it were a free body. The packing being deformed and confined between the members has all the characteristics of a free body and will be referred to as such.
. :'0 Under these cond1t1ons the packmgassumes substantially the cross sectional shape of the totally enclosed annular groove 4in which the packing is constrained when mating joint members are completely engaged. Thus the girth diameter of the packing when coni-ined between the members is greater adjacent the transverse shoulder of the male member.
The packing occupying an equal or slightly greater space when confined between the mem- 4( bers is not subjected to high mechanic-al stresses transmitted through the assembled joint duringy the use of the members as Aa part of a drill string or the like.
Any externalor internal fluid pressure seeking its way through the joint contacts the free packing body subjecting it to pressure. This-tendency initiates a ilowing action on the packing in the same direction as that of the pressure. 'Ihe packing being forcefully constrained tightly seals the walls of the closure and the adjacent surfaces of the male and female members, thus preventing the escape of fluid therebetween. The greater the uid pressure the tighter the seal is the nhvinug result unrlpr itl-men nnnrifinms Other advantages and objects will appear in the following description.
Referring to the accompanying drawings wherein I have illustrated a practical embodiment of the principles of my invention,
Fig. 1 is a longitudinal section of a pair of tool joint members in their assembled position showing the application of vthis invention.
Fig. 2 is an enlarged fragmentary section showing the relative positions of the'members when the female member engages the packing as they are being coupled to form a joint.
Fig. 3 is a view similar to Fig. 2 with the members being farther advanced to the coupled position, illustrating the flowing action on' the packing as it is being deformed.
Fig. 4 is a View similar to Fig. 2 with the members in their fully made up position.
Fig. 5 is an enlarged fragmentary view illustrating diagrammatically the relative cross sectional areas of the space that the packing occupies when normal and when deformed.
Fig. 6 is an enlarged view similar to Fig. 4 illustrating the tendency of the packing to flow when subjected to an external fluid pressure.
Fig. 1 is a View similar to Fig. 6 illustrating the tendency of the packing to flow when it is subjected to an internal fluid pressure.
Referring to Fig. 1 of the drawings wherein a conventional type of tool joint is shown, I represents 'the male or pin member of hollow cylindrical form and provided with a reduced coaxial portion having the threads II formed thereon, which portion may be tapered as shown. I2 represents a complementary female or box member having the mating threads I3 formed within its bore, which bore is coaxial with and complementary to the threaded portion of the pin member. The bores of the other ends of these members are provided with threads, as shown at I4, which,are arranged to receive complementary threaded portions of pipe sections which are not shown.
I represents an annular surface on the pin member between the threads II -and an annular groove I1 at the base of the transverse annular shoulder I6. The surface I5 may be a con'- tinuation of the plane o f the top of the threads II. The groove I1 is preferably of substantially semi-circular cross-section as` shown but may be of other form. I8 represents an annular packing ring of substantially' circular cross section arranged to be placed in thegroove I1. This packing is preferably made of resilient material such as rubber. The main requirement as to its characteristics is that it be flexible or pliable so that it will yield to fluid pressures and flow into available spaces creating a fluid seal therein.
The cross section of groove I1 is not completely semi-circular as may be noted by the space I9 between the circular shaped packing and the transverse shoulder I6. The inner end of the groove I1 is formed by the conical surface 20 which terminates at the shoulder I6, thus providing a smooth continuous path on which the packing may bey deformed into its proper shape to function as a seal when the joint is being formed.
This deforming action is illustrated in Fig. 3 wherein the packing has assumed a cross sectional shape resembling that of an ovoid. When the members are farther advanced to their fully made up position, as indicated in Fig. 4, the packing is deformed into cross sectional shape substantially equivalent to that of a sector.
The outer bore of the female or box member 1s provided with the annular surface 2l. This surface is complementary to the surface I5 and may be the continuation of the plane of the roots of the threads I3. The surfaces I5 and 2I may be tapered as shown, or may be cylindrical.
The end 22 of the member I2 is arranged to engage the shoulder I6 when the joint is properly made up. The unthreaded surface 2| and the surface of the end 22 are connected by an annular beveled surface 23 having a greater degree of taper than that of the surfaces I5 and 2l. This beveled surface may be termed the working surface of the packing as it works or rolls the packing into the desired shape and forms a part of the packing chamber wall.
The degree of taper of the surface 23 effects the'volume of the packing used. The volume of the enclosed packing chamber between the assembled members I0 and I2` must be equal or slightly greater than the volume of the packing used to avoid initial compression of the packing. Thus the angle of taper may be changed to vary the volume of the enclosed packing chamber.
The respective volumes of the packing and the chamber may be readily compared in Fig. 5.v `The segment 24 or the displaced portion of the packing is slightly smaller in area than the'area 25 which represents space between the surfaces I6,.
is on the outside of the drill pipe'.- This external pressure seeks its Way between thel shoulder I6 and the end 22 and contacts the free packing body I8, tending to force it ahead. The packing thus being under compression tends to be extruded between the members I0 and I2 on the low pressure side of the packing chamber forming the annular rib 26.
In Fig. 7 the highest fluid pressure is on the inside of the drill pipe. This internal pressure seeks its way through the threaded portions of the members and contacts the free packing body I8 tending to force it between the shoulders I6 and 22, thereby forming the annular rib 21 which seals the joint.
In both instances the compression of the packing by the fluid pressure forces it into-sealing engagement with the walls of the packing chamber, providing an initial or primary seal as compared to the seal produced by the extruded part of the packing which may be termed the secondary seal. These terms refer to time and space rather than efficiency.
With this invention an efficient seal is obtained. The packing when not under fluid pressure though deformed is practically a free body and will not lose its resiliency and consequently its efficiency because it is free of mechanical pressure from the members which enclose it. Again, mechanical stresses transmitted from one member to the other which form the joint have no effect on the packing. This relieves the packing from undue wear and mechanical working by the members, which ages the material and'causes it` `up, and a packing in said chamber of less volume chamber having diverging walls formed by said members when the joint is made up, and a packing member in said chamber having a volume less than the capacity of said chamber and ireel to lowin response to iiuid pressure whereby to wedge the packing against said diverging walls and thus seal the complementary surfaces of said joint.
2. In a seal for use in a joint connecting two coaxially alined members, thecombinatlon of an annular groove formed in one of said members and arranged to' be closed by the other member when the joint is made up to form a chamber, and
a resilient packing element in said groove having normally a diierent cross sectional contour-athen that of said groove and said packing element being shaped, but without material compression, toI conform to said groove by the second member when the joint is made up, said packing element having the characteristics of a free body to iiow in response to `iiuid pressure whereby to wedge `the packing against the converging walls of said chamber and thus seal the complementary surn faces of said joint.
3. 'In a seal for a joint between two coaxially aligned'frnembers, the combination of an annular chamber vhaving diverging walls formed by said members when the joint is made up, and a packing member normally of circular cross section in the chamber, the volume of which is less than the volume of said chamber, the packing being free to ilow in response to fluid pressure whereby to wedge the packing against said diverging walls to seal the same. y
4. In a seal for use in a joint connecting two coaxially aligned members, the combination of an anular chamber having diverging surfaces formed by said members when the joint is made than the capacity of the chamber, the normal cross sectional shape of said packing being dierent from that of the chamber, causing the packing to be reshaped without material compression when the joint is made up, said packing capable of being wedged by uid pressure between said `diverging surfaces to seal the joint.
5.- A rotary toolv joint including a socket, a pin having a threaded shank adapted to be screwed into said socket, and sealing means between the pin and socket comprising a ring of resilient material disposed in an annular groove formed in the threaded shank of the pin and partially projecting from said groove to be pressed into tight engagement with the wall of the socket as the pin is screwed therein, said ring being made of rubber and being normally of aA circular cross section, but in sealing position being distorted to a non-circular cross section.
6. A rotary tooljoint including a socket, a pin having a threaded shank adapted to be screwed into said socket, and sealing means between the pin and socket comprising a Aring oi resilient material disposed in an annular groove formed in the threaded shank of the pin and partially projecting yfrom said groove to be pressed into tight engagement with the wall of the socket as the pin is screwed therein, said pin having a shoulder at the outer end of the threaded shank, and said socket having a shoulder atl the outer end of its bore adapted to be engaged by theA shoulder of said pin when the pin is fully inserted in saidv socket, said groove being located adjacent the junction of said threaded shank and 'shoulder of said pin in the side wall of the pin.
lwERTON T. ARCHER.