There is described a device for thread protector comprising a protection body having a contact surface arranged to enclose a thread portion, more particularly by at least one locking device being provided inserted in the contact surface, as the locking device comprises a latch having a gripping portion and an operating portion, and where the gripping portion in the locking device's active state extends outward from the contact surface and the operating portion is arranged in a recess running into a surface opposite the contact surface.

For protection of threaded portions of pipe, such as drill pipe, thread protectors of various kinds are used.

In their simplest form a cap or a sleeve having internal threads corresponding to the external thread portion on the pipe is used for an exterior thread portion, as the cap is screwed onto the pipe . Correspondingly a plug having external threads is used for insertion in the end portion of the pipe having internal thread. The drawback with this kind of thread protectors is that it is time consuming screwing and unscrew- ing the thread protector on and off the pipe. Thread protectors of this type are often produced from a cheap material, such as plastic, and may be disposable protectors. They may also be produced from metal and may be provided with a lifting attachment for use when the pipe is lifted. Weatherford Klepo ^® represents another type of thread protectors, as this type is connected to the pipe by an internal cavity in the thread protector being filled with pressurised air so that a portion of the thread protector is forced against the pipe thread.

From US 4616679 is known a thread protector provided with an expandable friction portion arranged internally in a sleeve and arranged for releasable abutment against a portion of the external thread portion of the pipe. Operating a compression bar arranged to compress an element inserted in the internal wall of the sleeve and which upon compression ia expanding in a radial direction thereby activating the friction portion. A quick release mechanism arranged on the end surface of the sleeve is connected to the compression bar. The sleeve is also provided with a grooved portion to increase the friction between the thread protector and the pipe .

The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art.

The object is achieved by virtue of the features disclosed in the below description and in the following claims.

The invention provides a thread protector for external or internal threads, for example arranged in the end portions of a pipe, particularly pipes of the type used in building a drill string or for casing a well bore. There is obtained a protec- tion body having a contact surface facing the thread portion to be protected. The contact surface is preferably complementary to the shape of the thread portion, i.e. it may be cylindrical or cone-shaped. In the contact surface is arranged at least one locking device provided with a gripping portion, which in an operative position extends from the contact surface to locking engagement with the thread portion. The lock- ing device is also provided with an operating portion arranged in a recess running into a surface opposite the contact surface. The operating portion may, in the operative position of the locking device, be arranged flush with or inside the periphery of said surface. This is particularly advantageous for a thread protector for external threads . For a thread protector for internal threads it will be more advantageous if the operating portion extends out from the periphery of said surface to thereby simplify operation of the locking device. The locking device is preferably spring loaded toward its operative position. The gripping portion is preferably arranged with a sliding surface arranged to slide over the threads when the thread protector is moved in over the thread portion, and having a gripping surface arranged to go into locking engagement with at least one thread and prevent the thread protector being displaced away from the thread portion unless the locking device is operated to free its engagement with the thread portion. The thread protector may comprise means for closing a pipe run by an end wall be- ing integrated in the protector body.

By the expression "contact surface" is in this connection meant the shell surface on the protection body facing the thread portion. The shell surface need not necessarily be in direct contact with the thread portion itself, as said shell surface may abut one or more portions in the immediate vicinity of the thread portion, or possibly abutment portions extending out from said shell surface in such a way that the shell surface has a certain clearance to the thread portion.

The invention relates more particularly to a thread protector comprising a protection body having a contact surface arranged to enclose a thread portion, characterised in that at least one locking device is arranged in the contact surface, the locking device comprising a latch provided with a gripping portion and an operating portion, and where the gripping portion in the active state of the locking device extends out from the contact surface, and the operating portion is ar- 5 ranged in a recess running out into a surface opposite the contact surface. The thread protector may be mounted and dismounted by simple operations as the locking device is locked to and released from the thread portion without the thread protector having to be rotated. o The latch may be spring-loaded. This gives a secure engagement in the thread portion.

The locking device may be recessed into the contact surface. A contact surface is thereby provided without extending elements, which may prevent the displacement of the thread pro-s tector in over the thread portion, or be damaged by the threads .

The latch may be arranged, by displacement of the operation portion toward the contact surface, to displace the gripping portion into a recess in the contact surface. Unintendedo locking of the thread protector in the thread portion is thereby avoided at dismounting of the thread protector.

The gripping portion may be provided with a first side surface, which in the operative position of the thread protector faces away from a free end of the thread portion, and is ar-5 ranged to form an inclined plane toward the thread portion. Thereby the thread protector may be slid in over the thread portion without the locking device having to be operated.

The gripping portion may be provided with a second side surface facing the free end of the thread portion, and which iso complementary with a side surface of a thread. The protector body may be provided with a closed end portion. The advantage of this is that a pipe bore stretching between two thread portions may be closed so that ingress of foreign bodies or the like is prevented.

The thread portion may be an external thread portion, the contact surface being an internal shell surface in the protector body.

The thread portion may be an internal thread portion, the contact surface being an external shell surface in the pro- tector body.

In the following is described an example of a preferred embodiment, which is illustrated in the accompanying drawings, wherein:

Fig. 1 shows an end view of a thread protector for exter- nal threads according to a first embodiment of the invention;

Fig. 2a shows a longitudinal section II-II in fig. 1 through an end portion of a pipe having an external thread portion wherein a thread protector is ar- ranged according to a first embodiment of the invention;

Fig. 2b shows a longitudinal section through an end portion of a pipe having an internal thread portion wherein a thread protector is arranged according to a sec- ond embodiment of the invention;

Fig. 3 shows schematically and to a larger scale a detail of the thread protector being displaced onto an external thread portion; and Fig. 4 shows schematically a detail of the thread protector being removed from en external thread portion.

In the drawings the reference numeral 1 indicates a thread protector, which in a first embodiment, arranged for an ex- ternal thread portion 21 of a pipe 2, is shown as an end view in fig. 1 and in longitudinal section in figs. 2a, 3 and 4. In a second embodiment the thread protector 1 is arranged for an internal thread portion 22 and is shown in longitudinal section in fig. 2b.

The thread protector 1 is formed by a protector body 11 having a contact surface 111 arranged to cover the thread portion 21, 22. In the embodiments shown the pipe 2 is provided with cone-shaped thread portions, and the contact surface 111 exhibits a complementary, conical shape. It is within the scope of the invention that the contact surface 111 exhibits varying shapes according to what shape the thread portion 21, 22 to be protected exhibits.

Two diametrically opposite elongated recesses 113 extending in the axial direction of the protector body 11, are provided in the contact surface 111 and are arranged for rotatable fastening of a locking device 12. The locking device 12 comprises a latch 121, which in a mid-portion is attached to the protector body by means of a rotary shaft 125 arranged perpendicularly to an axial plane through the protector body 11. A compression spring 124 or some other flexible body is arranged between a spring abutment portion on the latch 121 and a bottom portion of the recess 113. Opposite the spring abutment portion 126 the latch 121 is provided with a gripping portion 122, which is arranged to extend outward from the contact surface 11 for engagement with the nearby thread portion 21, 22. The gripping portion 122 is provided with a sliding surface 122a facing away from a free end portion 211, 221 and is arranged to be able to slide on the thread portion 21, 22. Opposite the sliding surface 122a is arranged on the gripping portion 122 a gripping surface 122b arranged to be able to enter into locking engagement with the thread portion 21, 22.

The latch 121 is, opposite the gripping portion 122 provided with an operating portion 123 extending in the opposite direction to the gripping portion 122 through a recess 114 formed in connection with the recess 113 and running out in an external surface 112 on the protection body 11. By "external" surface is here meant the surface accessible for an operator when the thread protector 1 is arranged on the pipe 2. For an external thread protector (see fig. 2a) it means the outside surface, while for an internal thread protector (see fig. 2b) it means the inside surface.

On the external thread protector 1 the operating portion 123 is flush with the external surface 112, while the operating portion 123 advantageously extends out from the external surface 112 on the internal thread protector 1 to provide a fa- vourable operating function.

To take care of that a pipe bore 23 stretching inwards from the free end portions 221 of the pipe is protected against penetration of dirt etc., the thread protector 1 is preferably provided with an end wall 117, shown here only on the thread protector 1 for internal threads in the form of a plate body abutting supportingly against a land 119 and is fastened by means of a wall attachment, indicated here as a locking ring 118 arranged in a groove in the protection body 11.

When the thread protector 1 is moved in an axial direction into position over the thread portion 21, 22, and preferably to abutment with a land in the end of the thread portion 21, 22 or to abutment of the contact surface against the thread portion 21, 22, the locking device 12 may be unattended, as the sliding surface 122a of the gripping portion 122 slides 5 over the thread portion 21, 22. The latch 121 is forced against the thread portion 21, 22 by the compression spring 124, and the gripping surface 122b will enter into locking engagement with the nearest opposite thread in the thread portion 21, 22 thereby preventing the thread protector 1 to io slide out from the thread portion 21, 22.

At removal of the thread protector 1 the operating portion 123 of the latch 121 is forced inwards in the recess 114 effecting the gripping portion 122 to be pulled into the recess 113 for freeing the thread protector 1 from the thread por- i5 tion 21,22. The thread protector 1 may thereafter be displaced in an axial direction away from the thread portion 21, 22.