Patent Grant
7387713
The present invention generally relates to anode devices used to inhibit corrosion in metal water heater tanks and other metal liquid storage vessels and, in a preferred embodiment thereof, more particularly relates to a specially designed resistored anode assembly useful in this corrosion-inhibiting application.
Conventional metal water heater tanks, like other types of metal vessels used to store liquids, are subject to corrosion during use. To inhibit this corrosion, sacrificial anodes, normally constructed of magnesium, aluminum or zinc, are inserted into the tank. The sacrificial anode is slowly consumed during the corrosion protection process while generating an electrical current. AS the anode is slowly depleted, its simultaneously generated electrical current catholically protects the tank against corrosion.
The service life of the anode tends to be inversely dependent upon the amount of electrical current it generates in cathodically protecting the tank. In many fresh water supplies, particularly those having a high mineral content, the current flow generated by the anode is relatively high, resulting in a corresponding decrease in the useful life of the anode. In order to control the rate of consumption of a sacrificial anode, various anode constructions have been previously proposed in which a resistor is incorporated in the anode, and electrically connected between the anode and its protected tank, to automatically regulate the electrical current generated by the anode during its operation and thereby increase the service life of the anode.
While these resistored anode devices typically extended anode life, many of them also tended to be of a relatively complex construction, rather difficult to assemble, and relatively expensive to fabricate.
Many of these problems were essentially eliminated by a prior art sacrificial anode assembly that incorporated, in a simplified manner, an ordinary barrel-type carbon resistor into the interior of the assembly. This prior art anode assembly included a cylindrical plastic insulating sleeve captively retained within a metal cap portion of the anode assembly and having a closed end with a central opening through which an end portion of the metal anode body core rod extended. A diametrically extending groove, which intersected the central sleeve opening, was formed in the closed sleeve end.
The cylindrical resistor body was disposed in a radial portion of the sleeve end groove, with one of the resistor end leads being radially extended over the anode rod end and soldered or welded thereto. The other resistor end surface groove in the insulating sleeve end passed through an axially extending exterior side surface groove in the insulating sleeve and was soldered or welded at its outer end to an external metal cap portion of the anode assembly.
Although this method of operatively positioning a resistor in a sacrificial anode assembly provided a worthwhile reduction in assembly time and cost, and provided the desired regulation of anode current generation, it was found that it could create a problem relating to the structural integrity of the completed anode assembly. Specifically, it was found that in certain shipping orientations of the tank in which the anode assembly was installed, harmonic vibration might be created within the central anode core rod which were transmitted to the solder or weld joint connecting a resistor end lead to the rod. These vibrations could fatigue and break the rod/lead solder or weld joint, thereby rendering the anode assembly inoperative.
This vibration-created breakage of the rod/lead solder or weld joint was substantially eliminated by the anode assembly improvements incorporated in this type of anode assembly as illustrated and described in U.S. Pat. Nos. 5,256,267 and 5,334,299, each of such patents having been assigned to the assignee of the present invention. Such patents are hereby incorporated by reference herein in their entireties. The improvements illustrated and described in these patents comprise replacing the axial cap end groove with a generally U-shaped surface groove, forming a generally U-shaped bend in the resistor lead to be soldered to the anode core rod, placing the U-shaped bend portion of the resistor lead into the U-shaped surface groove, and then soldering or welding the outer end of the resistor lead to the anode core rod. This configuration and placement of the soldered or welded resistor lead extending along the closed plastic sleeve end provided the lead with a flexure capability that substantially eliminated vibration-caused breakage thereof at the lead/rod solder or weld joint.
However, a problem with this constructional approach was subsequently discovered. Specifically, during electrically conductive connection of the resistor lead to the anode rod (as by soldering or welding) the lead could be forcibly engaged with the bottom side of its associated sleeve groove and deflected outwardly therefrom in a manner such that when the sleeve was subsequently pressed into the metal cap of the overall anode assembly, the deflected lead could contact and electrically short out against the metal cap.
A means to prevent this undesirable electrically shorting effect was implemented by the manufacturer of the anode assembly by using a drop of an ultra violet light-cured adhesive onto the lead and the plastic sleeve. This gave a firm immediate bond of the lead wire to the plastic sleeve, thereby preventing movement of the lead wire during the lead wire/anode rod welding or soldering process. Examination of field failures indicated that this corrective procedure reintroduced the stress on the lead wire that had previously been relieved by the generally U-shaped bend in the lead wire. If there was any movement of the sleeve on the anode or movement of the anode within the sleeve, a substantial stress was placed on the lead wire adjacent the lead wire/anode rod weld or solder joint. This same phenomenon was encountered if the plastic sleeve absorbed water causing the plastic to swell in a manner forcibly moving the lead wire and causing breakage thereof, thereby rendering the anode assembly ineffective in providing corrosion to its associated tank.
As can be seen from the foregoing, a need exists for a solution to these constructional problems presented in a protective anode assembly of the type described above. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a specially designed resistored sacrificial anode assembly is provided for use in a metal liquid storage vessel, such as a water heater tank, to inhibit vessel corrosion.
The anode assembly may be secured to the vessel, to extend into its liquid filled interior, and representatively includes a sacrificial anode member having a core portion extending therethrough, and an electrically non-conductive insulating sleeve member illustratively formed from a plastic material and receiving a portion of the anode member, the sleeve member having an end wall section with a through-opening therein. A hollow metal cap receives the end wall section of the sleeve member, and the assembly further includes an electrical resistor having a body portion supported on the end wall section of the sleeve member and a lead wire conductively anchored, illustratively by soldering or spot welding, to the core portion and having a curved stress relieving portion, representatively having a generally U-shaped configuration, received in the through-opening.
The receipt of the stress relieving portion of the lead wire in the sleeve end wall through-opening inhibits this portion of the lead wire from being deflected outwardly away from the sleeve end wall during the soldering or spot welding process, or thereafter, and contacting and shorting out against the metal cap when the sleeve is subsequently inserted into the metal cap.
Preferably the insulating sleeve member has a side wall section perpendicular to its end wall section and having an exterior side surface groove which extends perpendicularly to the end wall section. A second lead wire portion of the electrical resistor extends through this side surface groove.
According to another aspect of the invention, the sacrificial anode assembly further comprises an electrically insulative member which is interposed between the insulating sleeve member end wall section and the metal cap and extending over the through-opening in the end wall section of the sleeve member. The electrically insulative member functions as an insulative barrier to prevent contact between the stress relieving curved portion of the resistor lead wire and the metal cap even if such lead wire portion is somehow deflected outwardly away from the end wall section of the sleeve member. Preferably, the electrically insulative member is of a plastic material and is of an annular wafer-shaped configuration, with the insulative member having a central opening that overlies and exposes the anode core/resistor lead wire solder or spot weld area.
Referring to
The resistored sacrificial anode assembly 10 is operatively installed in the top end wall 12a of a representative metal water heater storage tank 12, extends into the water-filled interior of the tank, and operates to cathodically inhibit corrosion of the tank. As cross-sectionally illustrated in
The anode member neck portion 18 is coaxially pressed into the open lower end 26 of a cylindrical, electrically non-conductive molded plastic insulating sleeve 28 having a top end wall 30 through which a central circular hole 32 is formed. When the anode neck 18 is pressed into sleeve 28, the core wire end portion 24a is received in the hole 32. As will be readily appreciated by those of skill in this particular art, sleeve 18 could be alternately formed from an electrically insulative material other than plastic if desired.
Sleeve 28, in turn, is pressed into a hollow cylindrical metal cap member 36 having an enlarged diameter head portion 38, and a hollow externally threaded body portion 40 threaded into the top tank end wall 12a as shown in
To control and maintain the protective anode current at a suitable level, the anode assembly 10 is provided with a barrel-shaped resistor 42 (see
According to a feature of the present invention, a through-opening 49 (see
Prior to the insertion of the sleeve 28 within the body portion 40 of the cap member 36, the resistor 42 is snap-fitted into the top end groove 48 of the sleeve 28, the U-shaped portion 44a of the resistor lead 44 is positioned in the upper sleeve end through-opening 49, an outer end portion of the lead 44 is spot welded, soldered, or otherwise conductively secured to the upper core wire end portion 24a, as at 50 (see
With the insulated annular wafer 51 secured in place atop the sleeve end wall 30, the anode member-supported sleeve 28 is then operatively inserted into the body 40 of the cap member 36. The completed anode assembly 10 is then ready to be threaded into the tank wall 12a as illustrated in
The resilience of the generally U-shaped stress relieving portion 44a of the resistor lead 44 received in the sleeve through-opening 49 protects the lead 44 from breaking at the spot weld or solder area 50 due to vibrational or other forces. Additionally, the unique provision of the through-opening 49 (within which the U-shaped portion 44a of the lead wire 44 is disposed before the lead wire/core wire spot weld or solder area 50 is formed) substantially inhibits the U-shaped lead wire portion 44a from being bent upwardly beyond the sleeve end wall 30 during the spot welding or soldering process since there is no portion of the sleeve end wall 30 that underlies and can exert an upward deflection force on the lead wire portion 44a. Further, due to the unique provision of the sleeve through-opening 49, moisture-caused upward expansion of the sleeve end wall 30 also does not tend to upwardly deflect the U-shaped lead wire portion 44a upwardly beyond the sleeve end wall 30. Additionally, the installed insulative wafer 51 (representatively of a thin plastic construction) acts as an insulative barrier that prevents contact between the lead wire 44 and the metal cap 36 even if for some reason the lead wire portion 44a was somehow subjected to an upwardly directed deflecting force during the assembly process or otherwise.
The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.
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| Number | Date | Country | |
|---|---|---|---|
| 20070125640 A1 | Jun 2007 | US |
