Sheave cable guarding and guiding device

A safety device for cable sheave installations, which provides cable guide assemblies which block hands and the like from being drawn in to be injured between moving cables and sheave wheels. The cable guide assemblies are pivotally attached to the outside ends of arms in turn pivoted at their inside ends from the sheave wheel support structure. The cable guides also prevent injury and property damage from cable jump, by guiding cables with large approaching fleet angles directly onto the wheels.

BACKGROUND OF THE INVENTION 
1. Field 
The field of the invention is guides and guards for cables directed by 
sheaves employed in the drilling and servicing of oil and gas wells. 
2. State of the Art 
In the drilling and servicing of oil and gas wells, apparatus is often 
lowered and raised by cables operating within boreholes extending deeply 
into the earth. Cables typically run from a winch through one or more 
sheaves changing the direction of the cable, ultimately directing it 
downwardly into the borehole. 
Two principal problems, both addressed by the present invention, are 
associated with deployment and retrieval of cable in the boreholes. The 
cables run in the vicinity of workmen, whose hands or other body 
appendages are too often seriously injured when caught between the moving 
cables and rotating sheave wheels. In other cases the cable is drawn out 
of the cable guiding groove provided about the circumference of the sheave 
wheel. This "jumping of the sheave" is very dangerous to operating 
personnel, and is destructive to the sheave structure. The running cable 
may quickly abrade through the sheave structure, releasing the cable to 
whip violently and dangerously out of control. The cable is in danger of 
jumping the sheave when it can approach the sheave not directly, but only 
at a substantial angle to the plane of the sheave wheel called a "fleet 
angle". 
One common operation is the retrieval of data from deep within boreholes. 
An instrument("sonde") is connected to an armored cable containing 
electrical conductors. The data measured by the sonde is sent up the 
conductors to the surface to be recorded and analyzed. The conductive 
cable is called a "wireline" in the industry, and the measurement of data 
from the borehole is called "wireline operations". In a typical wireline 
operation, the cable is deployed from a winch cable reel through a first 
rigging sheave located on the drilling rig floor. This sheave is called 
the floor sheave, and the line goes upward from it to a second sheave 
suspended from a block on or near the center of the top of the drilling 
derrick. This sheave is called the top sheave, and the line descends from 
it downwardly into the borehole. 
Safety hazard in this instance occurs at the floor sheave, which the cable 
runs through at about knee height. Drilling rig floors typically have poor 
and uncertain footing, being covered with oil, drilling mud, water and 
other well fluids, and frequently ice. A slipping workman reflexively 
reaches for support, often grasping the moving cable, which carries his 
hand into the sheave to be pinched between the running line and the 
rotating sheave wheel. Hands, arms, legs or clothing may be also ensnared 
and carried by the moving line into its confluence with the sheave wheel. 
On offshore oil platforms, the sheaves used for routine drilling and well 
service operations are frequently attached to the deck of the platform. 
Lines of differing sizes are used for various necessary functions in 
proximity to workmen. The number of sizes of running lines enhances the 
danger of limb and clothing entrapment. 
Sizeable fleet angles are more likely to develop on sheaves fastened to 
decks or bulkheads rather than on those suspended overhead on swivels. 
Although the swivel mount in theory causes the sheave wheel to become 
aligned with the plane of the approaching and departing cable, sizeable 
fleet angles are in practice still developed because of the complications 
of friction, and other imperfections in the swiveling process. The fleet 
angle problem, then, occurs both with swivel suspended sheaves as well as 
with floor or bulkhead mounted sheaves. 
The prior art discloses attempts to block the entry of hands or clothing 
from entering the sheave assembly to be pinched between the cable and the 
wheel, and to guide the cable sufficiently to prevent cable jump from the 
sheave. U.S. Pat. Nos. 775,118 and 1,242,656 each disclose a pair of cable 
guiding arms pivoted from sheave wheel mounting bodies or housings. Each 
pair of arms at its end distant from the housing joins with a fixed 
integral guiding loop. The cable engaging loop, being integral with the 
pivoted arm, restricts the usable angle of the cable guide. This can only 
be countered by enlarged guiding loop size, impairing its guiding and 
guarding performance. Accordingly, these cable guides are inherently 
useful only within limited ranges of cable position and angle of approach 
to the sheave wheel. In the disclosed embodiments, this limitation is 
countered by providing guide arms of excessive length, less effectively 
guarding against digit or limb entrapment between the sheave and the 
cable. When enlarged guiding loop sizes are employed, the guiding is so 
impaired that cable jump may often still be a danger. 
The fixed integral relationship between the guiding loops and pivoting 
arms, the length of the arms, the point of pivotal attachment to the 
housing, and the play allowed the cable within the loops, all must be 
selected to provide the best combination. The guiding and guarding 
performance is necessarily compromised to achieve a balance between these 
competing factors. The same disadvantage is also disclosed in U.S. Pat. 
No. 1,379,868, wherein the arms are brackets fixedly secured to the 
housing, from which cable guide sleeves are pivoted. This allows for no 
adjustment of position of the guide sleeves during operation. Some lateral 
guiding flexibility is provided by the use of very loose pivotal 
connections. No automatic adjustment of guide sleeve position is possible. 
The brackets must be positioned to accommodate specific angles of approach 
of the cable to the sheave assembly. 
U.S. Pat. No. 1,365,951 discloses a combination of a fixed cord guide and a 
pivoted arm carrying such a guide. Again, the guiding element is fixedly 
secured to the arm. Similar disclosures are found in U.S. Pat. Nos. 
346,084, 349,520 and 126,391. The latter two are adapted for chain 
sheaves, but nevertheless disclose pivoting arms with fixed guide elements 
at each end. 
None of the devices disclose embodiments capable of sufficiently versatile 
application to provide efficient, dependable guiding and guarding of oil 
and gas well wireline cables. 
BRIEF SUMMARY OF THE INVENTION 
The present invention eliminates or substantially alleviates the 
shortcomings and disadvantages of present guarding and guiding devices for 
sheave cables. The inventive device comprises a pair of cable guide 
assemblies, disposed about the cable at its entry and exit to the sheave 
assembly. Each guide assembly is pivotally secured to the outer end of an 
arm assembly, which is in turn pivoted at its other end from the sheave 
wheel supporting structure. The guide and arm assembly pivot axes are 
parallel, and both are perpendicular to the plane of the sheave wheel. 
Each assembly carries a through bore, loosely but closely accepting the 
cable and oriented to pivot always within the plane of the sheave wheel as 
the guide and arm assemblies pivot during operation of the device. 
In operation, the arm pivots to place the guide assembly at the cable, to 
there itself pivot to align the bore with the cable. The cable is guided 
by the bore into the plane of the sheave, and the guide assembly 
effectively prevents limbs or objects from being drawn with the cable into 
the sheave wheel. 
The pivot attachment points of the arms to the sheave wheel housing may be 
selected to accommodate particular shapes of housings. The two arm 
assemblies need not necessarily be pivoted coaxially from the sheave 
housing. However, many sheave and housing designs may be accommodated by 
pivoting both arm assemblies coaxially with the sheave wheel, the pivoting 
guide assemblies not theoretically required but compensating for 
variations in sheave and cable diameter and arm length. 
Advantageously, each arm assembly comprises a pair of side members 
extending on opposite sides of the sheave supporting structure. The guide 
assembly preferably comprises a pivot block assembly spanning between the 
outside ends of the side members. The block assembly comprises at least 
two separable parts. The cable guiding bore is split among the parts, so 
that the bore is opened upon separation of the parts, and so that the 
block may be installed around the cable from the side without access to 
the cable ends, with the cable passing through the reassembled circular 
bore. In one preferred embodiment, one of the block portions spans between 
the side members, and has an internally threaded central perforation in 
the plane of the sheave wheel. A similarly oriented cable mounting slot 
opens from the threaded perforation through one side of the block portion, 
so that it may be placed about the cable. The cable guiding bore is 
provided extending axially through an externally threaded bushing which 
mates with the internal threads in the integral block portion. The bushing 
is split into halves along a plane through the axis of the cable guiding 
bore, so that the bushing may be assembled with the cable through the 
bore. Mating dowel pins and bores in the two halves of the bushing permit 
assembly with the split thread closely aligned. 
It is therefore a principal object of the invention to provide a cable 
guard device preventing worker injuries at the junction of moving cables 
and rotating sheaves. Another principal object is to provide a guide which 
eliminates the peril of excessive fleet angles causing cable jumping.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
A cable guide and guard assembly 10 is illustrated in FIG. 1 installed upon 
a typical floor mounted sheave assembly 11. Identically constructed cable 
guide assemblies 12 and 13 engage cable 14 as it enters and exits the 
sheave assembly respectively. Sheave wheel 15 rotates about an axle 16 
journaled to rotate within sheave housing 17. Cable 14 is guided by a 
groove 18 provided about the circumference of wheel 15. As seen best in 
FIG. 2, cable 14 is guided into the plane of sheave wheel 15 through a 
bore 19 in each cable guide assembly. This precludes the cable from 
jumping from groove 18. Guide assembly 12 also prevents cable 14 from 
drawing workers' hands or clothing into the juncture 20 of sheave wheel 15 
and cable 14. 
The cable guide assemblies are supported by arm assemblies 21 and 22, 
respectively, connected pivotally by pairs of aligned axle stubs 23 
oriented parallel to sheave wheel axle 16. In this embodiment, the axle 
stubs each comprise unthreaded outstanding stem portions 26 of a shoulder 
bolt 24 installed within a threaded bore 25. 
Arm assemblies 12 and 13 comprise pairs of side members 27,28 and 29,30 
respectively. The side members are in this illustrated embodiment 
pivotally secured together at the axle 16 of the sheave wheel 15 by end 
flared sleeves 31 installed loosely fitting within aligned bores 32 and 33 
through joining side members 27,29 and 28,30. Each side member is 
advantageously shaped to provide end portions parallel to the plane of 
sheave wheel 15, both at sheave axle 16 and at each guard assembly 12 and 
13. Side member end portions of pair 27, 28 are offset inwardly, and those 
of pair 29, 30 outwardly, to interface in line with connecting side member 
sections 34,36 and 35,37 respectively. (FIG. 2) Interface washer 38 
prevents direct, potentially binding, frictional contact between the 
pivoting ends. (FIGS. 4 and 5) Axle pin 39 extends through hollow sheave 
axle 16, securing both arm assemblies pivotally to sheave assembly 11 
coaxially with sheave wheel 15. Axle pin 39 preferably comprises a 
contoured head 41 to mate with the outside flared end of the adjacent 
sleeve 31. Shaped retaining nut 42 similarly engages the other of the 
sleeves 31. With this arrangement, each arm assembly pivots independently 
of both the sheave housing and the other arm assembly. 
Each of the cable guide assemblies 12 and 13 includes a pivoting block 43 
spanning and securing the outside ends of the side members of each arm 
assembly together through shoulder bolts 24. The pairs of aligned shoulder 
bolts 24 secure the block 43 pivotally to the side members of each of the 
arm assemblies 21 and 22, along a line perpendicular to sheave wheel 15. 
Each shoulder bolt bore 25 has a counterbore 43 sized to closely accept 
the unthreaded stem portion 26 of the associated shoulder bolt. Shoulder 
44 bottoms, leaving sufficient space between end 45 of block 43 and bolt 
head 46 to allow free rotation of the joining side member. Thus, the cable 
guide assemblies 12 and 13 readily pivot to guide cable 14 during 
operation. 
As best seen in FIG. 5-9, the cable guiding bore 19 axially pierces 
externally threaded bushing 47, which is installed within an internally 
threaded perforation 48 through pivoting block 43. Perforation 48 is 
oriented so that its longitudinal axis is within the plane of sheave wheel 
15. Externally threaded bushings 47 advantageously carries an enlarged 
gripping knob 49 to facilitate installation. When bushing 47 is installed 
within the threaded perforation 48 of block 43, the axis of cable guiding 
bore 19 lies within the plane of sheave wheel 15. 
For installation of guard assemblies 12 and 13 upon cable 15, the threaded 
perforation 48 of block 43 is opened laterally by a cable installation 
slot 50 aligned with the plane of the sheave wheel. With bushing 47 
removed, block 43 is placed around the cable, using slot 50. bushing 47 is 
split into matching halves 51 and 52, each containing a semicircular 
groove 53. (FIGS. 5-9) For installation, the halves are separated and 
bushing 47 reassembled about cable 14, the grooves 53 matching to provide 
the cylindrical cable guiding bore 19. Expanding dowel pins 54 join 
aligned blind bores 55 and 56 to closely align the grooves 53 and the 
severed halves of the external threads 57. Bushing 47, thus installed 
around cable 14, is then threaded into block 43 to complete the 
installation of each guard 12 and 13. Advantageously, sets of two or three 
parallel threads are employed within block 43 and upon bushing 47, the 
threads having quite steep pitch, permitting very rapid installation. 
Preferably, block 43 and bushing 47 are advantageously constructed of a 
Nylon composition with additives such as molybdenum disulfide and 
graphite, providing high abrasion resistance and inherent lubricity, to 
minimize wear on both guide bore and cable, which for wireline operations 
incorporates signal and ground leads. 
Further embodiments than those specifically illustrated are within the 
spirit of the invention. For example, although it is advantageous, the arm 
assemblies 21 and 22 need not be pivoted from a common point upon sheave 
housing 17. Separate attachment locations may permit more advantageous 
placement of the guide assemblies 12 and 13 for variously shaped sheave 
housings 17. For similar reasons, nor is either of the arm assemblies 
necessarily pivotally attached coaxially with sheave wheel 15. (FIGS. 13 
and 14) 
The cable guide assemblies may be differently mounted than as illustrated 
from the ends of pivoting arm assemblies. For example, a pair of parallel, 
spaced apart, cable guard mounting plates 57 could be affixed to the 
outside of the sheave housing 17. (FIGS. 15-17) A pair of parallel guide 
slots 58 in the plates 57 accept shoulder bolt stub axles 24, so that the 
guard assemblies 12 and 13 may be moved along the slots as required by 
cable 14. To preclude excessive guide assembly canting from cables having 
pronounced fleet angles, large diameter "outrigger" washers 59 may be 
fixedly attached as by welds 60 to shoulder bolts 24. Advantageously, 
rotating bearings, not shown, could be provided about stems 26 of shoulder 
bolts 24, to act within guide slots 58. 
Other designs could be employed to allow installation of the guide 
assemblies upon the cable from the side without access to either of its 
ends. One such design is indicated in FIG. 18, providing a removable 
portion 61 of pivoting block 43 having the groove 53. Other embodiments 
(not illustrated) could employ two or more removable portions so that bore 
19 would be split into three or more grooves upon dis-assembly. 
The invention may be embodied in still other specific forms without 
departing from the spirit or essential characteristics thereof. The 
present embodiments are, therefore, to be considered as illustrative and 
not restrictive, the scope of the invention being indicated by the 
appended claims rather than by the foregoing description, and all changes 
that come within the meaning and range of equivalency of the claims are, 
therefore, intended to be embraced therein.