US3779347A

US3779347A - Cable catcher

Info

Publication number: US3779347A
Application number: US00240681A
Authority: US
Inventors: A Chevalier
Original assignee: Marathon Oil Co
Current assignee: Marathon Oil Co
Priority date: 1972-04-03
Filing date: 1972-04-03
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18
Also published as: JPS4915293A; GB1404408A; CA968130A; DE2316342A1; FR2178934B1; FR2178934A1; JPS522460B2

Abstract

A device for catching a cable, e.g., a downhole oil well pump power cable, to prevent reverse motion of said cable. The device catches the cable in a pair of wedge-type slips, preventing the cable from dropping down the wellhole during its withdrawal from the hole.

Description

United States Patent 1191 [111 3,779,347 Chevalier Dec. 18, 1973 [5 CABLE CATCHER 778,048 12/1904 Krebs 24/126 R 1,498,048 6/1924 Lee v. 188/653 X [75] Inventor: Arthur Chevaher, Cody 2,564,389 8/1951 Boehm et al 188/67 x I C a d] 2,991,526 7/1961 Kuebler 188/651 X [73] Asslgnee g g s on omp ny, m ay 3,467,224 9/1969 Curtis et al. 188/6511 97 [22] Filed Apr 3 l 2 Primary ExaminerGeorge E. A. Halvosa PP 240,681 Atmrney-J0seph C. Herring et al.

[52] US. Cl. 188/652, 24/126 R, 24/136 R,

182/5, 188/65.l, 188/653, 188/67 [571 ABSTRACT A device for catching a cable, e.g., a downhole oil well 7 pump power cable, to prevent reverse motion of said o cable. The device catches the cable in a pair of wedgetype slips, preventing the cable from dropping down [56] UNITE S S E X$ES SZiENTS the wellhole during its withdrawal from the hole.

1,165,583 l2/l9l5 Farmer l88/65.l 5 Claims, 6 Drawing Figures CABLE CATCHER CROSS REFERENCES TO RELATED APPLICATIONS The inventor knows of no related pending U.S. patent applications.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to the field of cablesupporting bond brakes and cable-pulling implements and, more specifically, to a means of preventing a cable from falling into a well during pulling operations, classi fied in US. Patent Office Class 188, Subclass 65.1.

Prior Art US. Pat. No. 133,870 to Marshall discloses a ropegrabbing device to be used as a portable fire escape.

U.S. Pat. No. 3,179,994 to Meyer et a1 shows a cablebraking mechanism designed to support a workman physically attached to a vertical cable at an elevated distance.

US. Pat. No. 3,467,224 to Curtis et al discloses a safety cable-clamping device for oil wells which is either pneumatically or hydraulically operated. The device must be either electrically or manually activated.

While several different types of cable-clamping devices have been disclosed in the prior art, no completely mechanical device designed to allow a cable to move freely in one direction while immediately braking said cable to movement in the opposite direction has heretofore been discovered.

SUMMARY OF THE INVENTION The device comprises generally at least one slip assembly mounted in a housing such that it does not interfere with the cable while the cable is being pulled from the well, but immediately engages and stops the cable upon any substantial motion in the reverse direction. A shock absorber is attached to the housing to reduce the immediate stress on the cable and the slip assembly during the braking operation.

The device is completely self-contained, requiring no external actuating forces.

DESCRIPTION OF THE PREFERRED EMBODIMENTS BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a cross-sectional side view of both the cable-catching braking device (a more detailed view of which is shown in FIG. 2) and the attached shock absorber (shown in more detail in FIG. 3).

FIG. 4 represents a cross-sectional side view of a cable-catching braking mechanism containing two slip assemblies.

FIG. 5 is a cross-sectional end view of a slip assembly mounted on a cable.

FIG. 6 is a cross-sectional side view of a slip assembly engaging a cable.

Apparatus The preferred embodiment of this invention is best described with reference to the drawings. A multitude of variations of this mechanical structure will be readily apparent to one skilled in the art upon a reading of this description. These variations are also intended to be included within the scope of this specification.

Referring now specifically to FIGS. 2 and 4, the braking mechanism and its appurtenances are mounted in and about a housing or support means 55. Two slip as semblies are mounted within the housing. Each slip assembly comprises: 1) a fixed brake element 42, 2) a slip element 45, and 3) a slip guide 48.

The fixed brake element 42 is permanently mounted on the housing. It has a face for contacting the cable, and is positioned such that its longitudinal axis is substantially parallel to the cable. The contacting face is contoured so as to substantially conform to the cable. Optionally this face may be roughened to provide a greater frictional force.

The slip element 45 is slidably mounted in facing relationship to the fixed brake element. This element has a face for contacting the cable, the face being contoured to substantially conform to the cable. Optionally this face may also be roughened. This slip element is free to slide at an acute angle to the forward direction of the cable, thereby not interfering with the cable while it is being pulled, but engaging the cable if it attempts to fall back into the hole. (The forward cable direction as used herein is meant the direction the cable travels while it is being pulled from the well. Conversely the reverse direction of the cable is the direction the cable travels while going into the well.)

The slip guide 48 is a fixed path within the housing designed to hold the slip element in position. Hence it is positioned at an acute angle to the forward direction of the cable, which angle is preferably from about 6 to about 15, more preferably from about 8 to about 12, and most preferably from about to about 10.5.

The slip assemblies are equipped with a release means for sliding the slip elements away from the cable so as to permit unrestricted motion in the reverse direction of the cable. Preferably the slip elements are connected in series with each other by means of a slip connector 50, and a slip release line 20 is connected to the uppermost slip element. When the slip release line is manually pulled, the slip elements travel up the slip guides, thereby preventing contact with the cable. This slip release line is threaded through pulley 26 and then suspended near the ground so that it may be manually operated.

The housing is provided with a side anchor 30 to support the device in a substantially upright position, and a lower anchor 38 to hold the device down. These anchors are preferably connected to strong, but somewhat flexible, cables, so as to allow some freedom of movement of the device. The cables are, in turn, connected to suitably strong objects.

The cable is introduced into the assembly by a pair of rollers, one rigidly-mounted 24 and the other flexibly-mounted 22. The flexibly-mounted roller is attached to the housing by means of arm 16, and arm 14 and compressive spring 12. The rigidly-mounted roller is attached to the housing by means of arm 18. The other end of the spring is attached to some fixed portion of the cable-clamping device, e.g. the connector element 58. The housing is equipped with a guard 35 for the rollers.

A slip floating spring 10 is attached at one end to the uppermost slip to relieve wear on the slip faces.

The housing is connected by means of a connector element 58 to a conventional shock absorber means. A preferred shock absorber means is a shock absorber as illustrated in FIG. 3. This shock absorber is contained within a housing 64, and is attached overhead to the oil derrick via eye bolt 60. The spring 62 is rigidly connected to the housing by connector 68, and slidably connected to connector element 58 by means of rod 66.

A support means is attached overhead to the shock absorber. This is preferably a cable attached at one end to the shock absorber and at the other end to any object of suitable strength.

Operation In the normal operation of this invention, the cablecatching device is attached to a cable prior to the cable being pulled from the well. The cable-catching device is then mounted above the wellbore by means of a vertical cable, one end of which is attached to the top of the shock absorber and the other end to some suitably strong overhead object, e.g. some portion of the oil derrick. The bottom of the device is preferably located from about to about 40 feet, above the wellbore opening, more preferably from about to about 30, and most preferably from about to about 22 feet. The device is suitably anchored both sideways and downwardly by means of

elements

30 and 38, respectively.

Slip release line 20 is engaged to allow the cable to be lowered into the wellbore. As is evident from FIG. 4, when the slip release line is engaged the cable cannot make contact simultaneously with both the fixed brake elements and the slidably-mounted slip elements.

Upon removing the cable from the well, the cable slides through the braking device so that the slidablymounted slip elements ride upon the cable, thereby producing a relatively slight frictional force at both the interface of the cable and the mounted element slip and the interface between the cable and the fixed brake element. Slip floating spring 10 has a compressive force such that the slidably-mounted slips are allowed to ride just slightly upon the cable. This minimizes wear on the faces of the slip assemblies.

As the cable is being removed from the well, various conditions can arise which will allow the cable to essentially free-fall back into the well. However, with the cable-catching device attached to the cable, as soon as the cable begins to fall back into the well, the slips engage (due to the frictional force ever present between the slip mechanisms and the cable). As the slips engage they travel down their acutely angular path, wedging the cable between the slip elements and the fixed brake elements. This immediately stops the back drop of the cable.

The main purpose of this shock absorber is to allow the slip assemblies to gently engage the cable while each stand of tubing is removed from the cable. (The cable is preferably attached to tubing, which is measured in lengths or stands, while it is being lowered into the hole, to provide it with support. The cable is removed from the hole by pulling the tubing; hence each stand of tubing must be disconnected from its adjacent stand as it reaches the surface). Without the shock absorber the slip assemblies would tightly engage the cable, requiring the operator to manually disengage the slip assemblies by means of the slip release line after each stand is removed. However, since the shock absorber permits the slip assemblies to only gently engage the cable, the slip assemblies are disengaged by merely resuming the pulling operations.

The shock absorber also greatly alleviates the force immediately placed on a free-falling cable when the cable-catching device stops the cable.

The shock absorber is adjusted such that the cablebraking device is allowed to drop preferably from about 5 to about 20 inches, more preferably from about 8 to about l6 inches, and most preferably from about 10 to about 14 inches. Hence the immediate stress placed on the cable and the cable-catching device is somewhat relieved. The shock absorber spring tension is preferably selected such that the spring is not elongated when the cable-catching device is not engaged.

Once the cable has again been suitably supported, the pulling operation may begin again. Upon pulling the cable back through braking mechanism, the slidably-mounted slip elements again slide upwardly to a position where'they apply only a slight force against the cable.

MODIFICATIONS OF THE INVENTION Conventional construction materials, e.g. carbon steel, are suitable for most applications of this device. Also, none of the dimensions set forth in the drawings are critical, but are only representative of the approximate size of a particular embodiment.

The number and size of the slip assemblies are dependent upon the maximum weight of the cable for which the device is desired to be used. Hence, one or more slip assembly units ranging in size from about seven to about eight inches in length can be used in conjunction with this invention.

The configuration of the slip elements is unimportant. For the particular embodiment illustrated in the drawings, the shape is a three dimensional trapezoid. However, many variations of this shape are easily envisioned.

The basic device may be used in conjunction with cables of any practical size. Overall dimensions and strength conditions may be altered for the various cable sizes encountered. A major determinate, other than overall strength characteristics, as to whether the given cable is suitable for a given device is whether there is sufficient surface area contact between the slip assemblies and the cable circumference.

It is sufficient to point out that any conventional type shock absorber may be used in conjunction with this invention.

This invention is not intended to be limited by specific embodiments taught herein. Rather it is intended that all equivalents obvious to those skilled in the art be incorporated within the scope of this invention as defined in the specification and the appended claims.

What is claimed is:

1. A self-contained cable-clamping device for permitting a cable to move in a substantially vertical forward direction while rapidly clamping said cable in response to movement in a reverse direction, comprising in combination:

a. a housing;

b. two slip assemblies mounted within said housing,

each comprising:

1. a fixed brake element mounted on said housing, said fixed brake element having a contacting face for contacting said cable, said contacting face lying in a plane substantially parallel to said cable and being contoured so as to substantially conform to said cable,

2. a slip element slidably mounted in facing relationship to said fixed brake element, said slip element having a face for contacting said cable, said face being contoured to substantially conform to said cable, said slip element being free to slide at an acute angle to said forward direction travel of said cable, so as to engage said cable in response to cable movement in said reverse direction; and

3. a slip guide mounted on said housing for holding slip element in said position, said guide being mounted at an angle of about 8 to about l2 with respect to the reverse direction of the cable,

c. a spring attached at one end to the uppermost slip assembly and at the other end to a fixed portion of said cable-clamping device whereby said slidably mounted slip elements ride just slightly upon said cable to relieve wear on the cable contacting faces;

d. a shock absorber means connected to said housing for absorbing shock when said slip assemblies clamp said cable moving in said reverse direction;

e. a support means connected to said shock absorber means and said housing to support said cableclamping device in position, and:

f. a release means for sliding said slip element of said slip assemblies away from said cable so as to permit unrestricted motion of said cable in said reverse direction.

5 2. The device of claim 1 wherein the cable contacting face of the fixed brake element is roughened.

3. The device of claim 1 wherein the cable contacting face of the slide element is roughened.

4. The device of claim ll wherein the slip guide is 10 mounted at an angle of about 9.5 to about 10.5 with respect to the reverse direction of the cable.

5. The device of claim 1 wherein said support means comprises:

a. an overhead cable attached to said shock absorber means and to a suitably strong object;

b. a side anchor attached to said housing and flexibly connected to a suitably strong object so as to allow some freedom of movement of said device; and

c. a lower anchor attached to said housing and flexibly connected to some suitably strong object so as to hold said device down during forward motion of said cable.

Claims

1. A self-contained cable-clamping device for permitting a cable to move in a substantially vertical forward direction while rapidly clamping said cable in response to movement in a reverse direction, comprising in combination: a. a housing; b. two slip assemblies mounted within said housing, each comprising: 1. a fixed brake element mounted on said housing, said fixed brake element having a contacting face for contacting said cable, said contacting face lying in a plane substantially parallel to said cable and being contoured so as to substantially conform to said cable, 2. a slip element slidably mounted in facing relationship to said fixed brake element, said slip element having a face for contacting said cable, said face being contoured to substantially conform to said cable, said slip element being free to slide at an acute angle to said forward direction travel of said cable, so as to engage said cable in response to cable movement in said reverse direction; and 3. a slip guide mounted on said housing for holding slip element in said position, said guide being mounted at an angle of about 8* to about 12* with respect to the reverse direction of the cable, c. a spring attached at one end to the uppermost slip assembly and at the other end to a fixed portion of said cable-clamping device whereby said slidably mounted slip elements ride just slightly upon said cable to relieve wear on the cable contacting faces; d. a shock absorber means connected to said housing for absorbing shock when said slip assemblies clamp said cable moving in said reverse direction; e. a support means connected to said shock absorber means and said housing to support said cable-clamping device in position, and: f. a release means for sliding said slip element of said slip assemblies away from said cable so as to permit unrestricted motion of said cable in said reverse direction.

2. The device of claim 1 wherein the cable contacting face of the fixed brake element is roughened.

3. a slip guide mounted on said housing for holding slip element in said position, said guide being mounted at an angle of about 8* to about 12* with respect to the reverse direction of the cable, c. a spring attached at one end to the uppermost slip assembly and at the other end to a fixed portion of said cable-clamping device whereby said slidably mounted slip elements ride just slightly upon said cable to relieve wear on the cable contacting faces; d. a shock absorber means connected to said housing for absorbing shock when said slip assemblies clamp said cable moving in said reverse direction; e. a support means connected to said shock absorber means and said housing to support said cable-clamping device in position, and: f. a release means for sliding said slip element of said slip assemblies away from said cable so as to permit unrestricted motion of said cable in said reverse direction.

4. The device of claim 1 wherein the slip guide is mounted at an angle of about 9.5* to about 10.5* with respect to the reverse direction of the cable.

5. The device of claim 1 wherein said support means comprises: a. an overhead cable attached to said shock absorber means and to a suitably strong object; b. a side anchor attached to said housing and flexibly connected to a suitably strong object so as to allow some freedom of movement of said device; and c. a lower anchor attached to said housing and flexibly connected to some suitablY strong object so as to hold said device down during forward motion of said cable.