Anode and method of construction

An anode having an elongated body which may be extruded contains a bore extending at least partially through the body. The bore has an intermediate portion between the ends of the anode. A lead wire in the bore is fastened to a connector member having a self-tapping thread engageable at predetermined torque with the surface of the bore at the intermediate portion for cutting a thread in the bore upon relative rotation of the connector member and the body of anode material. A sealant is inserted in the bore after a thread is cut in the bore and surrounds the left in place connector member preventing moisture from reaching the connection to the anode at the intermediate portion.

This invention relates to the construction and method of making anodes for 
cathodic protection and especially to anodes where the connection is 
placed deep in the interior of the anode. By locating the connection at a 
position near the center of the anode, the corrosion consumption which 
tends to attack the anode sooner at the ends than between the ends, known 
as "end effect" or "pencilling", will not expose the connection to 
moisture which causes premature failure. 
Heretofore a center-connected anode has been proposed having two half 
sections with abutting ends threaded over a connector to position the 
connector in the center of the anode. In another proposed construction, 
the bore of the anode was drilled with a threaded portion at or near the 
center so that a connector could subsequently be threaded in the anode. 
These constructions have presented difficulties in sealing and protecting 
the connection where the anode is in sections and the seam at the center 
must be sealed without increasing the corrosion consumption in that area. 
Where the anode was not in sections, there is a problem in drilling a 
straight hole through an anode of from 36 to 150 inches (91 to 381 
centimeters) in length. It has also been difficult to tap threads at the 
center to receive a threaded connector. It is then a problem to engage the 
threads deep in the bore without cross-threading or stripping which has 
resulted in a weak unsatisfactory connection. 
The extrusion of the anode body has also not been considered feasible 
because the extruded body is usually slightly curved and this has 
presented problems particularly in long anodes in providing a bore with 
the features desired such as a good, strong, tight connection at the 
center portion, ease of manufacture and assembly. 
It is, therefore, an object of this invention to provide an anode 
construction in which the connector member has a self-tapping thread for 
cutting a thread in the bore to make a connection at a center intermediate 
portion of the anode. 
Another object is to provide anti-rotation surfaces on the connector member 
when the anode body or connector is being rotated to cut the thread in the 
bore. 
A further object is to provide an anode bore with an enlarged diameter from 
one end to an intermediate portion of the anode. 
A still further object is to provide a tapered self-tapping thread on the 
connector member for cutting a thread and making a strong tight connection 
with the anode body. 
Another object is to provide an anode construction with an extruded 
one-piece body. 
A further object is to provide a connector member configuration to limit 
the extent of the thread cut in the bore. 
Another object is to provide a method of making an anode in which the anode 
body is made with a bore, a connector member with self-tapping threads is 
brought into engagement with the surface of the bore and the anode body is 
rotated relative to the connector member to cut threads in the bore and 
produce a good tight connection. 
A further object is to provide a method in which the bore is reamed out 
from one end to an intermediate portion to provide an enlarged bore and 
shoulder for receiving the connector member. 
A still further object is to provide a method in which the anode body is 
extruded with a hole through its elongate axis. 
Another important object is to provide a method in which the relative 
rotation of the anode body and the connector member is stopped at a 
predetermined torque for providing both the desired predetermined length 
of thread cut in the bore and the desired electrical conductivity between 
the connector and body. 
A further object is to provide a method in which the rotation of the anode 
body relative to the connector member is stopped by a non-threaded portion 
on the connector member. 
To the accomplishment of the foregoing and related ends, the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims, the following description and the annexed 
drawings setting forth in detail certain illustrative embodiments of the 
invention, these being indicative, however, of but a few of the various 
ways in which the principles of the invention may be employed.

Referring to FIG. 1, an anode body 10 for an anode suitable for cathodic 
protection is shown. The anode body 10 may be of a suitable anode material 
such as graphite and be extruded in tubular form with a bore 11 extending 
from a first end 12 to a second end 13. The anode body 10 may have a 
length of from 15 to 150 inches (38 to 381 centimeters) and be slightly 
curved as a result of the extrusion process. The curvature is shown 
somewhat exaggerated in FIG. 1. The bore 11 formed during the extrusion 
may have a diameter "d". 
Referring to FIG. 2, a sectional view of an anode 14 incorporating the 
anode body 10 is shown with the first end 12 and second end 13 broken away 
from a center intermediate section 15 having an intermediate portion 16 of 
the bore 11. 
As shown in FIG. 2, the bore 11 is reamed from the first end 12 to the 
intermediate section 15 forming a distinct shoulder 20 at the approximate 
longitudinal center of the anode. After reaming, the bore from end 12 to 
the shoulder 20 has an enlarged diameter D through which a connector 
member 17 may be moved from such first end 12 to the intermediate section 
15 of the anode body 10. 
As seen also in FIG. 3, the connector member 17 includes a sleeve 18 of 
copper or other suitable electrically conductive and malleable material 
and a truncated cone-shaped plug 19 of suitable bar stock or die cast 
material such as zinc or brass fastened to the sleeve 18 as by brazing or 
silver soldering at joint 22. As shown in greater detail in FIGS. 3 and 4, 
the plug is provided with self-tapping threads 23 and a flute 24 with a 
cutting face 25. 
In the embodiment shown, the threads 23 have a 60.degree. thread angle and 
a pitch of 0.1 inch (0.254 centimeters). The self-tapping threads 23 also 
are on a tapered surface of the plug 19 and have a taper angle "a" of 
approximately 3.degree.. A square head 26 extends outwardly from the plug 
19 and is engageable by a socket-type wrench or other tool for holding the 
connector member 17 during assembly of the anode 14. The anti-rotation 
head 26 shown is square; however, this may also be hexagonal or of other 
suitable configuration or in the form of a recess or socket as long as 
suitable anti-rotation surfaces are provided. 
As shown in FIG. 2, the connector member 17 is positioned in the 
intermediate section 15 with the self-tapping threads 23 seated in threads 
cut in the surface of the intermediate portion 16 of the bore 11 at the 
shoulder 20 to provide a tight strong connection. A lead wire 27 extends 
from the second end 13 through the bore 11 to the connector member 17 
where it enters the sleeve 18 and is held in the sleeve by crimping of the 
sleeve or other suitable swaging operation. The lead wire 27 may be 
covered with insulation 28. It is believed apparent that the lead wire is 
threaded first through the smaller then larger bores of the anode to be 
attached to the plug as indicated before the plug is inserted to form the 
threaded connection. 
To seal the connector member 17 from moisture, a sealant 29 of suitable 
water-proofing material such as various low viscosity epoxy or asphaltic 
temperature or air setting materials is poured or injected into the bore 
11 from the first end 12 and second end 13. A long proboscis tool may be 
employed in this regard. 
Referring to FIGS. 2 and 3, the anode 14 is constructed so that the 
connector member 17 may be inserted into the enlarged portion 32 of the 
bore because the enlarged diameter D of the bore is greater than the 
maximum diameter D1 of the connector member 17. At the same time the 
enlarged diameter D is greater than the smaller diameter "d" of the bore 
11 in the intermediate portion 16 so that the self-tapping threads 23 will 
engage the surface of the bore at the shoulder 20. The minimum diameter D2 
of the self-tapping threads 23 is less than the diameter "d" of the bore 
11 at the intermediate portion 16 so that the plug 19 may project into the 
bore 11 and be positioned partly in both bores at the shoulder following 
the tapping operation. 
Referring to FIGS. 1-4, the method of making the anode 14 includes forming 
the anode body 10 with the longitudinal axis bore 11. This may be done by 
extruding the anode body 10 through a die into a configuration shown in 
FIG. 1. The enlarged portion 32 of the bore 11 is provided by reaming the 
bore from the end 12 to the intermediate section 15 which is the 
approximate center of the anode body 10. If desired, a pilot may be 
mounted on the reaming tool to follow the bore 11 and keep the enlarged 
portion 32 centered with respect to the anode body 10. The lead wire 27 is 
preferably threaded through the bore and then fastened to the connector 
member 17 by crimping the sleeve 18. 
The connector is then inserted into the anode body 10 through the enlarged 
portion 32 of the bore 11. A socket wrench or similar tool with a flexible 
extension for the longer anodes is engaged with the anti-rotation head 26 
and the self-tapping threads 23 are urged into engagement with the surface 
of the bore 11 at the shoulder 20 in the intermediate portion 16. Relative 
rotation of the anode body 10 and connector member 17 is provided so that 
the cutting face 25 of the threads 23 are moved into cutting engagement 
with the surface of the intermediate portion 16 of the bore 11 to cut 
threads in the surface. This relative rotation may be provided with long 
anodes preferably by holding the connector member 17 stationary while the 
anode body 10 is rotated. The relative rotation is continued until the 
torque required reaches a predetermined amount. The torque may be 
determined with a conventional torque wrench such as a one which 
free-wheels at the set torque. This is correlated with the desired amount 
of thread cut in the surface of the intermediate portion 16 of bore 11 to 
provide a strong tight electrical connection, but not so tight as to cause 
fracture or disintegration of the anode body. 
With the tapered self-tapping threads 23, it can be seen that the more the 
connector member 17 is turned relative to the anode body the deeper the 
threads will be cut. The torque required will also be greater. After the 
connection is made between the connector member 17 and anode body 10, the 
sealant 29 is inserted in the bore 11 from the ends 12 and 13 to surround 
the connector member. 
Referring to FIG. 5, a modification is shown in which the lead wire 127 
extends through the anode body 110 from the first end 112 to the second 
end 113. The connector member 33 has a plug 119 and a sleeve 118 like the 
plug and sleeve shown in FIGS. 2 and 3; however, in addition the plug 119 
has an additional sleeve 34 of metal such as copper which is crimped on 
the section of lead wire 127 extending through the enlarged portion 132 of 
the bore 111 from the first end 112. As shown in FIG. 5, the sleeve 34 is 
connected to the plug 119 by the braze or silver solder joint illustrated 
and is positioned adjacent but offset from an anti-rotation head 35 for 
engagement by a driving tool during the assembly of the anode 36. The 
precise configuration of the head and sleeve is shown more clearly in 
FIGS. 9-11. The method of making this anode 36 is the same as the method 
described hereinabove for the anode 14 of FIG. 2. The leads 127 will be 
connected to the connector before it is inserted for the tapping 
operation. After the self-tapping threads 123 cut the threads in the 
intermediate portion 116 of the bore 111, the space surrounding the 
connector member 127 in the bore 111 and enlarged portion 132 is filled 
with the sealant 129. 
Referring to FIG. 6, a modified connector member 37 is shown in which the 
plug 219 has self-tapping threads 223 with a partially tapered lead 
portion 38 and a cylindrical trailing portion 39. The self-tapping threads 
223 on the tapered portion 38 have a taper shown as angle "b" which is 
approximately 3.degree.. In all other respects, the connector member 217 
is like the connector member of the embodiment shown in FIG. 3 with an 
anti-rotation head 226 and with the sleeve 218 secured to the plug or body 
as by brazing or soldering at joint 222. The configuration of the 
connector ensures against overtightening. The extent of penetration into 
the reduced diameter bore may be controlled, rather than by a torque 
reading, by the number of relative revolutions. This embodiment would 
normally be employed only where the I.D. of the reduced diameter bore can 
closely be controlled with confidence at the shoulder. 
Referring to FIGS. 7, 9, 10 and 11, another modification is shown which is 
similar to the anode 14 of FIGS. 2, 3 and 4, and the anode 36 of FIG. 5. 
In this particular embodiment, the anode body 310 has a bore 311 which 
does not extend through the body from the first end 312 to the second end 
313 but terminates in a reduced diameter section 315 near the center. The 
bore of section 315 may be drilled first and the enlarged portion may be 
formed by a reaming operation. The reduced diameter portion 315 of the 
bore 311 has a smaller diameter "d" than the diameter D of the enlarged 
portion so that the connector member 317, which has a plug 319 with 
self-tapping threads 323, may be inserted through the enlarged portion and 
into engagement with the surface of the reduced diameter portion 315 at 
the shoulder 320 for cutting threads in that surface. 
A sleeve 334 is mounted on the end of the plug 319 with an anti-rotation 
head 35 alongside but offset from the sleeve as shown in FIGS. 10 and 11. 
The lead wire 327 extends through the enlarged portion 332 and into the 
sleeve 334 which is crimped to the lead wire before insertion and tapping 
to provide the necessary contact. In the assembly of this anode 42, the 
connector member 317 is inserted in the second end 313 and through the 
enlarged portion of the bore with the plug 319 entering the reduced 
diameter portion 315 of the bore 311 at the shoulder 320. The head 335 is 
gripped to prevent turning of the connector member 317 and the body of the 
anode 310 is rotated to cut threads in the surface of the reduced diameter 
portion 315 of the bore to provide a strong tight connection. Following 
this, a sealant 329 is inserted or poured through the second end 313 into 
the enlarged portion of the bore 311 to surround the exposed end of the 
connector member 317 and lead wire 327. 
Referring now to FIG. 8, a modified connector member 43 is shown having a 
sleeve 418 and a plug 419 secured together by soldering or brazing at 
joint 422 and self-tapping threads 423. This connector member 43 is 
similar to the connector member 17 of FIG. 3 except a non-threaded 
cylindrical portion 44 is provided at the larger end of the tapered plug 
419. The non-threaded cylindrical portion 44 has a diameter D3 equal to 
the maximum diameter of the tapered threads 423 so that when the connector 
member 43 is moved into engagement with the reduced diameter or 
intermediate portion 16 of the bore 11 as shown in FIG. 2 and relatively 
rotated with respect to the anode body 10, the extent of rotation and the 
length of the threads cut in the surface of the intermediate portion is 
limited by the cylindrical portion. In this way, the operator will know 
when the desired threads are cut by the sudden resistance of the 
cylindrical portion 44 to rotation of the connector member 417 and anode 
body 10. 
With reference to FIGS. 9-11, the modification shown is the same plug as 
shown in FIG. 7 in which a connector member 317 has a plug 319 connected 
to sleeve 334. An anti-rotation head 335 is formed on the plug but offset 
from the sleeve 334. The driving tool engaging the anti-rotation head 335 
may be cut away on one side for clearance of the crimp sleeve 334 and the 
wire lead connected thereto. In any event the embodiments of FIGS. 5, 7 
and 9-11 permit the lead wire to extend from one or both ends of the anode 
for connection to a power supply or series connection with other anodes 
and a power supply, as shown when comparing FIGS. 7 and 4, respectively. 
FIGS. 9 and 11 also illustrate clearly the chip clearance channel and 
cutting edge of the self-tapping plug. 
Although the illustrated embodiments of the present invention illustrate 
the crimp sleeve to be brazed or soldered to the plug, it will be 
appreciated that the material of the plug may be sufficiently malleable so 
that a hollow nose probe may be integrally formed in the plug into which 
the anode lead wires may be inserted and mechanically crimped. 
Also, while several forms of self-tapping plug are illustrated, the 
preferred form is the continuous uniform taper of FIGS. 2-4, 5, 7 and 
9-11, particularly when extruded hole anode material is employed. Such 
continuous taper plug has the ability to accommodate a number of inside 
diameters in the minor orifice bore. With an extruded hole, the diameter 
may change as the extrusion die wears and is changed. Such tapered thread 
allows accommodation to a substantial variation in the I.D. of the minor 
orifice bore. 
Also, it should be noted that the deeper the plug cuts into the anode, the 
greater the torque required relatively to turn the plug or anode. The 
amount of torque required directly inversely affects and thus becomes a 
measure of the electrical contact resistance of the connector to the 
anode. Therefore at a certain minimum torque, there will be assured a 
connector-to-anode resistance well below conventional connections. Thus 
the predetermined torque achieves both an excellent electrical connection 
and also avoids fractures or stress in the system. 
Further, while it will be appreciated that the self-tapping feature of the 
present invention greatly facilitates the connection deep into the anode, 
it should also be apparent that such self-tapping feature can be employed 
anywhere along the bore and much nearer an end than at the center. If the 
connector is tapped into the end of the anode, even though higher torque 
is usually required, the reaming or counter bore operation may be avoided. 
An anode connection near the end, although not providing an anode with the 
longest possible service life, is obviously less expensive to manufacture. 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the invention, it will be apparent to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the invention.