Gripper blocks for reeled tubing injectors

An improved gripper unit for use in an injector for handling coil tubing, pipe, rod, cable, or similar elongate objects, this gripper unit being provided with gripping surfaces which contact the coil tubing in V-block fashion and thus will grip such tubing of differing diameters. This gripper unit will enable the injector to support a given load while applying less squeeze. In the case of handling coil tubing or pipe, the stresses induced by these improved gripper blocks are very considerably reduced as compared with conventional gripper blocks.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to well tools, and more particularly to gripper 
units for use in injectors for coiled or reeled tubing, or similar 
elongate objects. 
2. Related Art and Information 
Reeled or coil tubing has been run into wells for many years for performing 
certain downhole operations such as, for instance, washing out sand 
bridges, circulating treating fluids, setting downhole tools, cleaning the 
internal walls of well pipes, conducting producing fluids or lift gas, and 
a number of other similar remedial or production operations. In addition, 
such injectors have been found useful in performing operations in 
horizontal and slanted wells. 
Use of such reeled or coil tubing saves much time and money because the 
reeled tubing injectors force the reeled tubing into the well through a 
seal such as a stripper head, and may do so continuously and at a good 
rate of speed. Since the tubing is in one piece, time is not lost in 
having to make up a threaded connection about every 20 to 30 feet (6.1 to 
9.14 meters) such as when jointed pipe is used. Further, such injectors 
can be moved to be jobsite, set up, and moved off the job much quicker and 
less costly than can drilling rigs or workover rigs. 
Many such reeled tubing injectors are in common use today and a number of 
patents relating thereto have been issued. Typically, most of the reeled 
tubing injectors utilize a pair of opposed endless drive chains which are 
arranged in a common plane. Such drive chains are made up of links, 
rollers and gripper blocks. In some cases gripper inserts are used. These 
drive chains are generally driven by sprockets powered by a motor, such as 
a reversible hydraulic motor. The opposed drive chains grip the reeled 
tubing between them. These drive chains are backed up so that a goodly 
number of pairs of opposed gripping blocks are in gripping engagement with 
the tubing at any given moment. As the chains are in motion and the tubing 
is being driven, each time a pair of gripper blocks is actuated to release 
their hold on the tubing another pair is actuated to gripping position. 
The moving drive chains are thus able to force the tubing into the well, 
or to remove the same therefrom depending upon the direction in which they 
are driven. 
A number of patents have been issued relating to reeled or coil tubing 
injectors. Among those are the following U.S. Pat. Nos.: 
2,679,924 3,258,110 3,285,485 3,559,905 
3,754,474 4,515,220 4,655,291 
U.S. Pat. No. 2,679,924 which issued to P. R. Powell on June 1, 1954 for 
"STRAND-ADVANCING APATUS" discloses an apparatus employing a pair of 
opposed drive chains each having a multiplicity gripping shoes for 
gripping and moving a strand, cable, or the like, as the chains are 
driven. The gripper shoe 20 is shown in FIG. 5 to have a concave groove 
for engaging and gripping the cable, or the like, being moved. This groove 
has a radius slightly larger than the radius of the largest object to be 
moved. (Col. 2). 
U.S. Pat. No. 3,258,110 issued to D. W. Pilcher on June 28, 1966 for 
"ENDLESS CHAIN APATUS". This patent discloses opposed drive chains 
having gripping elements 15 with concave gripping surfaces. (Col. 2 and 
FIG. 2). 
U.S. Pat. No. 3,285,485 issued to D. T. Slator on Nov. 15, 1966 for 
"APATUS FOR HANDLING TUBING OR OTHER ELONGATE OBJECTS". This patent 
discloses drive chains including gripper units (FIG. 6-7) which are 
connectable one to another by the pins 15 which also pass through the 
chain links 11a and rollers 11b. (Col. 3, line 10 et seq.). This U.S. Pat. 
No. 3,285,485 is hereby incorporated herein for all purposes. 
U.S. Pat. No. 3,559,905 issued on Feb. 2, 1971, to Alexander Palynchuk for 
"METHOD AND APATUS FOR RUNNING AND PULLING A CONTINUOUS METAL MEMBER 
INTO AND OUT OF A WELL". This patent discloses a track assembly 2 
including opposed sprocket chains 10 each having gripping pads 11. (Col. 
4, lines 42, et seq.) (FIGS. 10-12). Elements 41 which frictionally grip 
the rod 4 "will preferably be made of somewhat flexible material in order 
that it may be used with rod strings of varying diameters. An element 
formed of urethane elastomer having a Shore durometer range of D-50 has 
been shown to be suitable." (Col. 5, lines 32-39). 
U.S. Pat. No. 3,754,474 issued to Alexander Palynchuk on Aug. 28, 1973 for 
"GRIPPER PAD". This patent discloses a gripper unit for use in an 
apparatus such as that disclosed in U.S. Pat. No. 3,559,905, just 
mentioned. This gripper unit includes "a gripper pad 3 which includes a 
block 4 having studs 5 embedded therein. (Col. 2, lines 33-34). Block 4 is 
of a deformable elastomer material (line 43) and studs 5 are "of a metal 
softer than steel, preferably aluminum or aluminum alloy." (Col. 3, lines 
6-16). U.S. Pat. No. 3,754,474 is incorporated into this application by 
reference for all purposes. 
U.S. Pat. No. 4,515,220 issued on May 7, 1985 to Phillip S. Sizer, Don C. 
Cox, and Malcolm N. Council for "APATUS AND METHOD FOR ROTATING COIL 
TUBING IN A WELL". This patent discloses a reeled or coil tubing injector 
which can handle coil tubing and also handle jointed pipe on the upper end 
thereof, even rotate it in a well. While the gripping blocks on the chains 
will grip both the coil tubing and the quill through which the pipe is 
run, the grippers grip only one size. Their gripping surfaces are concave 
or semi-circular in section. The quill is provided with ridges which are 
the same radius as the coil tubing. (See in FIG. 17 coil tubing 50 and in 
FIG. 20 the quill 75). This U.S. Pat. No. 4,515,220 is incorporated herein 
by reference for all purposes. 
U.S. Pat. No. 4,655,291 issued to Don C. Cox on Apr. 7, 1987 for "INJECTOR 
FOR COUPLED PIPE". The disclosed apparatus utilizes the same type of drive 
chains and gripper blocks as does the apparatus of U.S. Pat. No. 4,515,220 
just mentioned. This U.S. Pat. No. 4,655,291 is incorporated herein by 
reference for all purposes. 
Publication "DEEP EARTH SAMPLING SYSTEM-PHASE I", Final Report of National 
Science Foundation, dated June 1990 and published by MAURER ENGINEERING 
INC., Houston, Tex., discloses various concepts for handling tapered 
strings of coil tubing. These concepts are: use of stacked injectors, each 
adapted for a different size of tubing (page 20); an injector having two 
independent mechanisms to handle two sizes of tubing (page 21); gripper 
units having three sizes of gripper grooves side by side for handling 
three sizes of tubing. The drive chains of this apparatus would need to be 
shifted laterally for each diameter change (page 21); and gripper blocks 
for accommodating two sizes of tubing through providing gripper blocks for 
small tubing with a second, larger radius to fit a larger diameter tubing 
(page 26). 
None of the prior art of which applicant is aware teaches or suggests 
gripper blocks for reeled or coil tubing which will provide an adequate 
grip with less squeeze and which will grip tubing or similar objects of 
various sizes. 
Grippers for reeled or coil tubing generally have been formed either from 
an elastomeric material which would conform to the shape of the tubing 
exterior and take a friction grip thereof, or formed of steel and provided 
with notches having a radius slightly greater than that of the tubing. 
These steel grippers took a vise-like grip on the tubing and although they 
fit the tubing fairly closely, excessive squeeze often resulted in the 
tubing being distorted to an out-of-round condition and scarred. The 
problem was that the squeeze was applied to the tubing at two points 
opposite each other at 180 degrees apart. Early failure of the tubing and 
the stripper seals is understandable. 
Such grippers are used extensively today, and since it is known that they 
can distort and scar the tubing, and since longer strings of tubing are 
needful in the industry, it has been desirable to provide improved 
grippers for reeled tubing which will overcome the shortcomings of the 
existing grippers, and at the same time readily grip tubings of various 
diameters. The present invention is an improvement over the gripping 
blocks used in the known prior art and overcomes many of the shortcomings 
associated therewith, and are more suitable for use in the modern oil 
industry where wells are deeper, conditions more severe, operations more 
costly, and damaged or ruined reeled tubing can cause considerable delays 
and added costs. 
SUMMARY OF THE PRESENT INVENTION 
The present invention is directed toward a gripper block for use in 
grippingly engaging a coil tubing, pipe, rod, cable, or the like object 
for applying a longitudinal load thereto, such gripper block having means 
at or near its opposite ends for attachment to an endless chain of an 
injector apparatus, the gripper block having a pair of gripper surfaces 
formed thereon, these gripper surfaces being elongate surfaces and tilted 
toward each other to diverge, toward the tubing to be gripped, at 
approximately 90 degrees. These gripper surfaces thus provide a V-block in 
effect. In one embodiment of this invention the elongate gripper surfaces 
are provided with multiple grooves providing multiple gripper ridges 
running crosswise thereof, that is, relative to the tubing axis. 
It is therefore one object of this invention to provide an improved gripper 
block for use in an injector apparatus which is provided with a pair of 
flat gripping surfaces which are tilted with respect to one another to 
form a V-groove for receiving the tubing to be gripped. 
Another object is to provide a gripper block of the character described 
having crosswise grooves formed in the gripping surfaces to provide ridges 
for contacting the outer surface of the tubing. 
Another object is to provide such a gripper in which the two gripping 
surfaces are separated slightly to provide a flat or similar surface at 
the bottom of the V-groove. 
Another object is to provide a gripper block of the character described 
which will grip tubing, pipe, cable, or the like, of various diameters. 
Other objects and advantages will become apparent from reading the 
description which follows and from studying the accompanying drawings 
wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, it is seen that a reeled or coil tubing injector 
is shown schematically. The coil tubing injector is indicated generally by 
the reference numeral 25 and is shown gripping a coil tubing 30. 
A pair of endless drive chains 32 each carrying a multiplicity of gripper 
blocks 34 are shown on opposite sides of the coil tubing 30. The gripper 
blocks are pressed against the coil tubing by hydraulic cylinders 36 
biasing the pressure beams 38 inwardly through trunnions 40. A roller 
chain 42 is interposed between the pressure beams 38 and the drive chains 
42 to reduce friction therebetween. 
It is easy to see that the drive chains 32 are actuated by sprockets 44 
which are powered as by reversible hydraulic motors (not shown). Idler 
sprockets 46 take up slack in chains 32. 
It is readily seen that many pairs of opposed gripper blocks 34 along the 
pressure beams are in contact with and grip the coil tubing at any one 
moment during the time that the pressure beams 38 are pressed toward each 
other by the hydraulic cylinders 36. The squeeze thus applied to the coil 
tubing by the gripper blocks is varied by adjusting the hydraulic fluid 
pressure. 
Referring now to FIG. 2, it will be seen that a gripper block such as that 
used on the apparatus 25 of FIG. 1 is shown and is indicated by the 
reference numeral 34. This gripper block is seen in the end view of FIG. 3 
to have a concave or semi-circular gripping surface 50 and that this 
gripping surface is provided with spaced apart grooves 52, seen in FIGS. 2 
and 4 which leave ridges or lands 54 therebetween. These grooves and lands 
provide a better grip on the coil tubing; the lands engage the outer 
surface of the tubing, distributing the stress over a large area while 
providing higher unit loading at the lands. At the same time, the grooves 
provide space for the accommodation of oil, grease, paraffin, and other 
materials which may be carried on the coil tubing and displaced as the 
lands grip the tubing's outer surface. 
The radius of curvature of the gripping surface 50 is preferably slightly 
greater than the radius of the coil tubing. 
Referring now to the schematic view of FIG. 5, it is seen that a coil 
tubing 60 is engaged on opposite sides by gripper blocks 34a which may be 
exactly like the gripper blocks 34 of FIG. 2. The gripper blocks are shown 
applying inwardly directed forces to the tubing at opposite locations 
indicated by the reference numerals 62 and 63. Inwardly directed forces of 
a given value thus applied to the tubing through the gripper blocks enable 
the apparatus to support an axially directed load of given value to which 
the tubing is subjected. Insufficient squeeze may result in slippage; and 
excessive squeeze may result in damage to the tubing. 
The inward bias of the gripper blocks 34a induce stresses into the tubing 
at the points 62, 63 which are 180 degrees apart. The radius of the 
gripping surface 64 is slightly greater than that of the tubing outer 
surface. In FIG. 6, the diagram of the bending moments induced into the 
tubing 60 as a result of such inwardly directed loads are represented by 
the curves at 62a and 63a. The ordinates of these curves 62a and 63a, as 
seen at 62b and 63b, for instance, represent to scale the resulting 
induced bending moments. 
It is readily seen that there is a tendency for such forces to distort the 
tubing, that is, to bend the wall thereof and mash the tubing out of 
round. 
On the other hand, the ordinates at 65 and 66 indicate a tendency for the 
tubing wall to bulge outwardly at those locations which are located 90 
degrees from points 62, 63. 
Gripper blocks of this invention do not tend to distort the tubing so 
readily as might the gripper blocks seen in FIGS. 3-6. 
Gripper blocks of this invention are shown schematically in FIG. 7 where 
they are indicated by the reference numerals 71 and 72. Gripper block 71 
is provided with gripping surfaces 74, 74a. Gripper block 72 is provided 
with gripping surfaces 75, 75a. These gripper surfaces of each gripper 
block are tilted with respect to each other to diverge toward the tubing 
to form an included angle of approximately 90 degrees. The opposed gripper 
blocks 71, 72 are shown applying inwardly directed forces to a coil 
tubing, such as coil tubing 60 to effect a frictional grip. These inwardly 
directed gripping forces are directed at four locations spaced at 90 
degrees around the tubing, as at points 71a, 71b, 72a, and 72b. Thus, 
these inwardly directed forces are noticeably much better distributed 
about the tubing than were the two opposed inward forces in the case of 
FIGS. 5 and 6. 
In FIG. 8, the bending moments induced into tubing 60 as a result of such 
inwardly directed forces are shown by curves 76a, 76b, 76c, and 76d. The 
ordinates of these curves as seen at 77a, 77b, 77c, and 77d represent to 
scale the resultant induced bending moments. 
It is readily understood that the gripper blocks of FIG. 5 are much more 
apt to apply inwardly directed forces which would exceed the yield 
strength of the tubing than would the gripper blocks of FIG. 7. 
Comparing the maximum moment ordinate, M.sub.A, seen in FIG. 6 with the 
maximum moment ordinate, M.sub.B, seen in FIG. 8, it is seen that the 
gripper blocks 71, 72 of FIG. 7 greatly reduce the induced stresses over 
those induced by the gripper blocks 34a of FIG. 5. If M.sub.A =0.3183 and 
M.sub.B =0.0683, then M.sub.A divided by M.sub.B would equal 4.66. 
This means that the bending stresses induced by the two-point loads, as in 
FIG. 5, are 4.66 times as great as those induced by the four-point loads, 
as in FIG. 7. 
Further, it is noted that since each of the gripper blocks 71, 72 has a 
pair of gripper surfaces 75 which are tilted to form an included angle of 
90 degrees and thus contact the tubing 60 at two points 72a, 72b which are 
45 degrees from the centerline passing through the point where the pair of 
gripping surfaces meet, then the load applied to the gripper block is 
divided in two and applied at this 45 degree angle. Thus, the four point 
load applied to the tubing 60 in FIG. 7 is only about 70 percent that of 
the load applied to the tubing 60 in FIG. 5. Thus, if the load applied by 
each of the gripper blocks in FIG. 5 is Q, then the load applied by each 
of the gripper blocks in FIG. 7 is 0.707Q. 
Thus, if the two-point load is Q, the four-point load will be 0.707Q, or 
70.7 percent. 
Thus, the gripper blocks of this invention provide the necessary grip or 
load-holding power with only about 70 percent of the lateral loading or 
squeeze on the tubing. 
Not only do the gripper blocks of this invention permit less squeeze for 
the same axial-load capacity, but this understandably translates into less 
damage to the tubing and longer life therefor, as well as making its use 
safer. 
Further, the gripper blocks of this invention are capable of engaging and 
supporting tubing, or similar elongate objects, of differing diameters, 
and this without shifting anything, even the gripper blocks themselves. 
Referring now to schematic FIGS. 9-12, it is seen that a pair of gripper 
blocks 100 are shown gripping a tubing 102 of say one-inch (2.54 
centimeters) in diameter and providing four-point loading as discussed 
hereinabove. Similarly, the same gripper blocks 100 are shown in FIG. 10 
gripping a tubing 104 of say 1.25 inches (3.175 centimeters) in diameter 
and similarly in FIG. 11 the diameter of tubing 106 is say 1.5 inches 
(3.81 centimeters) in diameter, while similarly in FIG. 12 the diameter of 
the tubing 108 is say 1.75 inches (4.445 centimeters). 
In each case shown in FIGS. 9-12, it is clear that the conditions are the 
same, that the four-point loads are applied in the same manner, and that 
the four points are always 90 degrees apart and 45 degrees from the center 
of the V-grooves. It is clearly shown that the gripper blocks 100 are 
adapted to engaging tubings having an appreciable range of diameters. 
A gripper block of this invention is illustrated in FIGS. 13-16 where it is 
indicated generally by the reference numeral 150. 
In FIG. 13 it is seen that the gripper block 150 is provided with a body 
152 having a tongue 154 with a pin hole 156 extending transversely 
therethrough. In FIG. 14, the gripper block 150 is seen to be turned 
end-for-end or 180 degrees. A pair of spaced-apart ears 158 provide a slot 
160 therebetween which is adapted to receive the tongue 154 of another 
adjacent gripper block. The ears 158 are each provided with a pin hole 162 
and these holes are aligned. When two such gripper blocks are mated with 
the tongue 154 of one in position between the ears of the other, a pin can 
be placed in the aligned holes 156 and 160 to flexibly connect the two 
gripper blocks together so that they may articulate. Many such links are 
connectable together to form a chain such as that used in a coil tubing 
injector, for instance, such as that seen in FIG. 1. 
Since the gripper block 150 is a complete gripper unit only one pin will be 
needed for each gripper block. 
Although the gripper portion of the gripper block could be formed 
separately and then secured to the main body portion, it is preferable to 
form the gripper block in a single piece since its ability to grip various 
sizes of tubing fairly obviates replacing the drive chain when a tubing of 
different diameter is to be handled. 
The gripper block illustrated in FIGS. 13-16 is formed with a V-groove as 
at 170 providing planar surfaces 170a and 170b which are tilted relative 
to one another. It is preferable for these two surfaces 170a to form an 
included angle of approximately 90 degrees, however other similar angles 
would work but with lesser efficiency. Thus, the gripping surfaces of each 
of the gripper blocks 150 will engage the exterior of a cylindrical 
object, such as a tubing, at two points, as seen in FIGS. 7 and 9-12, the 
pair of gripping blocks clearly providing four-point contact. Where these 
slanted planar gripping surfaces are let to remain without grooves, they 
would grip the tubing but grease, paraffin, mud, dirt, and other such 
material might interfere with the efficiency, dependability, and safety of 
their performance. 
Preferably, these slanted gripping surfaces 170a and 170b are each formed 
with a suitable number of grooves such as groove 172. These grooves 172 
extend perpendicularly to the longitudinal axis of the gripper block body 
and are spaced apart to provide suitable ridges, such as at 174 for 
engaging the tubing. The grooves 172 provide space for receiving the 
grease, paraffin, mud, et cetera, which may be carried on the tubing's 
exterior and which may be displaced therefrom in the gripping operation. 
These ridges 174 and grooves 172 are preferably shaped to provide adequate 
strength. As illustrated in FIGS. 13 and 14, the ridges 174 and grooves 
172 have a profile resembling the thread form of an Acme thread. (An Acme 
thread has sloping sides with flats at both crests and roots.) Preferably 
this profile approximates a Acme thread having four threads per inch (25.4 
millimeters). The profile of these ridges and grooves may, however, be 
designed to fit particular needs if desired. 
The V-groove 170 formed by the tilted gripping areas 170a and 170b may stop 
short of intersecting, as seen in FIG. 15, if the gripper blocks will not 
be required to grip tubing of very small diameter. Therefore, the V-groove 
170 is preferably formed with a ridgeless bottom surface which may be 
flat, as shown at 180, or concave, as desired. 
Preferably, the grooves 172 separating the ridges 174 are spaced apart from 
about 0.18 inch (4.57 millimeters) to about 0.38 inch (9.7 millimeters), 
but may be formed as desired. 
The ridgeless area 180 at the bottom of the V-groove preferably is formed 
with a width about 7 to about 30 percent the width of the gripper body 
means, but certainly may be formed as desired. 
In FIG. 17, a modified form of gripper block is illustrated and is 
indicated generally by the reference numeral 200. It is formed with first 
and second ends, 200b and 200c, and with first and second sides, 201a and 
201b. Gripper block 200 is very similar to the gripper blocks disclosed 
hereinabove differing only in its ears; the V-groove gripping means 170a 
is the same as the gripping means 170 of the gripper block 150. Gripper 
block 200 is provided with but one ear on each of its opposite ends. Thus, 
as shown, an ear 202 is provided at the first end 200b and a like ear 204 
is provided at the second end 200c of the gripper block. Both of the ears 
202, 204 are shown on the second side 201b of the gripper block, as seen 
in FIG. 16 and are substantially half as wide as the gripper block. Each 
of these ears is provided with a suitable hole for receiving a pin 206 
when assembling the gripper block in a drive chain. Since both of the ears 
202, 204 are on the same side of the gripper block, an identical block can 
be turned around so that both of its ears are on the left side so as to 
become mateable with either end of the gripper block 200. 
A fragment of phantom upper and lower gripper blocks are shown assembled to 
each end of gripper block 200. These phantom gripper blocks are both 
identified by the reference numeral 200a. It is clearly shown that the ear 
202a of upper gripper block 200a is positioned next to gripper block 200 
so that the holes (not shown) thereof are in alignment and that pin 206 
links the gripper blocks together in chain fashion. Similarly, ear 204a of 
lower gripper block 200a is linked to ear 204 as by pin 206a. 
It is readily understood that in the manufacture of gripper blocks, such as 
gripper blocks 200, the holes can be formed more economically and in less 
time with, perhaps, less expensive and/or less sophisticated tooling. It 
is particularly important that it is not necessary in such case to drill, 
grind, or otherwise form aligned holes in two spaced apart ears, such as 
the spaced apart ears 158 of the gripper block 150 of FIGS. 13-14. 
Referring now to FIG. 18, it is seen that another modified form of gripper 
block is illustrated and is identified by the reference numeral 230. 
Gripper block 230 is generally similar to the gripper block 200 just 
described with respect to FIG. 17, being formed with first and second 
ends, 230b and 230c, and with first and second sides, 231a and 231b. 
Gripper block 230 is provided with an ear 232 at its upper right corner as 
seen in FIG. 18 and this ear 232 is exactly .like the ear 202 on gripper 
block 200. Gripper block 230 is similarly provided with an ear 234 at its 
lower end, but at its lower left corner. Thus, ear 234 is at the opposite 
corner from ear 232, and is not on the same side of the gripper block as 
in FIG. 17. Ears 232 and 234 are identical and interchangeable. 
In assembling gripper blocks such a grippe block 230 in chain fashion, all 
of the links are oriented the same way and it is not necessary to turn one 
of the gripper blocks around. Thus, in FIG. 18, upper and lower phantom 
gripper blocks 230a are shown assembled to gripper block 230. The ear 234a 
of upper gripper block 230a is linked by pin 206 to ear 232 of gripper 
block 230, and similarly, ear 232a of lower gripper block 230a is linked 
to ear 234 of gripper block 230 in the same manner by pin 206a. Since the 
gripper block 230 has but one ear on each end, it, like gripper block 200 
previously described, lends itself well to modern mass production 
processes, such as molding, metal powder molding, casting, or the like 
processes. 
The V-groove means for gripper blocks such as those disclosed hereinabove 
may be formed as a separate part and afterwards secured to a body means by 
suitable means, such as welding, brazing, bonding, or the like, or through 
use of blots, screws, or the like, or through use of dovetail slots, or 
similar securing means. 
In FIG. 19, it is seen that V-groove means 300 comprises a body 302 having 
formed thereon a V-groove 304 and with grooves 306 and ridges 308 which 
function in a manner which is identical to those illustrated and described 
hereinabove, for instance, such as V-grooves 170, grooves 172, and ridges 
174 of FIGS. 15 and 16. After forming such V-groove means, by machining, 
or casting, molding, or the like, it is secured to body means 310 by 
suitable means as at 312. The complete gripper block thus formed is then 
ready for assembly into an endless chain for use in a machine such as a 
coil tubing injector such as that illustrated in FIG. 1, for instance. 
It has been shown that the improved gripper body of this invention fulfills 
all of the objects set forth hereinabove and provides distinct advantages 
over the known prior art. It is understood that the foregoing description 
of the invention and the illustrative drawings which accompany the same 
are presented by way of explanation only and that changes in the shape of 
the gripper and arrangement of its elements may be had by those skilled in 
the art without departing from the true spirit of this invention.