US3353850A - Method and apparatus for holding a pair of hollow metal articles together - Google Patents

Description

Nov. 21, 1967 T. E. BUTZ ETAL 3,353,850

\ METHOD AND APPARATUS FOR HOLDING A PAIR OF HOLLOW Y METAL ARTICLES TOGETHER Filed Nov. 9, 1966 Fig. I

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United States Patent 3 353 850 METHOD AND APIARATUS son HOLDING A PAIR OF HGLLOW METAL ARTICLES TOGETHER Tom E. Butz, Chagrin Falls, and Seymour N. Schlern,

University Heights, Ohio, assignors to The Farmer Manufacturing Company, a division of Textron Inc, Cleveland, Ohio, a corporation of Rhode Island Filed Nov. 9, 1966, Ser. No. 593,197 1 Claim. (C1. 285-284) ABSTRACT OF THE DISCLOSURE A joint between a pair of radiator or boiler sections which sections each have tapering passages to their interiors wherein a conventionally shaped push nipple with a curved outer surface is employed. The nipple is coated with a thin heat resistant plastic coating. The radiator sections are forced over the coated push nipple and the resulting joint includes areas of metal to metal contact between the push nipple and the radiator passages, as well as areas of plastic forced into the interstices between the outer surface of the push nipple and the passages of the radiator sections. On opposite sides of the area having both metal to metal contact and plastic forced into the interstices there are areas completely bridged over by the plastic which are essentially free of metal to metal contact.

was-- This is a continuation-in-part of application Ser. No. 442,684, filed Mar. 25, 1965, and now abandoned. This invention relates to a method and apparatus for holding boiler and radiator sections together and for providing a fluid connection therebetween.

Heretofore it has been common practice in the art to manufacture radiators, which comprise a plurality of sections, by making the sections singly and then securing a number of the sections together to provide a radiator of the desired capacity. Likewise, boilers have been made in the same general manner. Since it is necessary that the sections also have means for circulating the steam or other fluid through the sections each section is provided with ports which are in alignment with those of the other sections, and reversely threaded nipples are threaded into the ports to provide the fluid connection. The threaded nipples are expensive both to manufacture and install and had the additional disadvantage that the radiator sections could not be placed as close together as desired, thus increasing the space and decreasing the heat exchanging capabilities.

It has also been common practice to provide a radiator where the nipples which connect the sections called push nipples are not threaded but have a double tapered outer wall which fitted into the tapered wall of the ports and radiator or boiler sections and wherein the sections are pushed together under pressure to cause the nipples to seal in the bosses. Such radiators were then held assembled by bolts which extended from one end of the radiator to the other. Such a device is shown in Patent No. 1,384,606. Among the problems encountered in the above push-nipple devices is the requirement that very close alignment of the nipple receiving bosses must be maintained, otherwise the nipples would cant and provide an imperfect seal. Also, surface imperfections on the nipples and radiator bores as well as out of tolerance surfaces and bores contribute to a certain number of leaking seals with the above devices. In addition, through holes in the boiler or radiator sections must be provided for allowing the bolts to extend therethrough, which necessitates a coring operation during casting and increases the cost of manufacture. The alignment of these holes must also be held to very close tolerances. In addition, it requires more time to assemble the radiators, as well as the provision of the through bolts, both of which are expensive. In an attempt to eliminate the problems of sealing with push nipples, it has been proposed to provide a lead sleeve over the nipple, as shown in Patent No. 908,985, of Jan. 5, 1909. Although this provides some improvement in the seal, lead is of a slippery nature and has no holding power. Once lead is deformed, it stays deformed. Therefore, it was still necessary to use the through bolts to hold the sections together because of the complete lack of holding power.

The present invention contemplates a method and apparatus whereby a nipple of the push type may be used and because of its operation the radiator or boiler sections are secured together without the use of any bolts, clamps or means other than the nipple itself.

Still other advantages of the invention will become more apparent from the following description of an embodiment thereof, which is illustrated by the accompanying drawing, and forms a part of this specification.

In the drawings:

FIGURE 1 is a vertical medial sectional View of a nipple used in carrying out this invention on a greatly en- I larged scale with certain features exaggerated to better illustrate its form;

FIGURE 2 is a fragmentary sectional view of a pair of boiler or radiator sections with the nipple in position joining them together in fluid tight relationship, also with certain features exaggerated for clarity; and,

FIGURE 3 is a somewhat diagrammatic representation of a portion of the interface between an assembled push nipple and passage wall in a radiator section.

Briefly, this invention contemplates the provision of a push nipple formed of a relatively malleable material, such as malleable iron, which has an adhesive coating on the surface thereof, preferably a cured synthetic resin, which nipple is inserted in the nipple receiving bosses of adjacent radiator or boiler sections and when the sections are forced tightly over the nipple the nipple will provide a fluid tight connection between the radiator or boiler sections with the nipple providing for fiuid communication between the hollow interiors of the adjacent sections. The push nipple provides the sole structural connection between the radiator or boiler sections without the necessity of using tie bolts or the like.

More particularly, and referring now to the drawing, and for the present to FIGURE 1, a medial sectional view of a push nipple for use in this invention is shown on a greatly enlarged scale with the outer curvature thereof exaggerated for clarity of illustration. The push nipple per se is comprised of a tubular malleable iron body member 10 having a through central bore 12 and a curved or tapered outer surface 14. The body 10 is of conventional design configuration. In this design, the outer surface 14 from the outer edges 16 inwardly to points 18 is formed with a radius of curvature R and the surface between the points 18 is formed with a radius of curvatures R R being greater than R It is to be understood that the radii R and R used to illustrated these curves are actually much shorter proportionally to the body 10 than are actually present in the nipple, thus exaggerating these two curves in the drawing to illustrate the outer configuration of the body 10. This combination of a larger radius R than radius R provides for a flatter curve between the points 18 at the mid-portion of the nipple and a steeper curvature toward the outer edges of the nipple. This configuration also provides for a greater thickness of the body 10 at its central portion than at its outer edges.

The exterior curved surface 14, as well as the end surfaces 20, of the body is coated with a layer of adhesive 22. The adhesive is preferably one of the plastics having the ability to withstand water, steam or other heat exchange liquids. It should have the ability to expand and contract along with the material of the body and to fill the pores on the surface of the body as well as the pores of the section to which it is to be engaged. Although shown as covering the outside surfaces only, it is con templated that the entire outside and inside could be coated with the adhesive. It is also preferred that the adhesive be of a character that the aging of the adhesive be such that it attain a certain degree of hardness. Also, the adhesive should have the ability to fiow at the time of installation. When the adhesive finally stabilizes, it should be a semi-rigid material. Suitable adhesives include, but are not limited to synthetic resins in the classes including polypropylene, urethane, epoxy resins, and the hydrocarbons.

FIGURE 2 shows a pair of radiator or boiler sections 24 in assembled relationship with an adhesive coated push nipple. Each of the sections has a boss 26 which is provided with a tapered frusto conical inner surface 28 having one end 30 communicating with the interior of the section and an opposite end opening 32. The diameter of the opening 32 is greater than the diameter of the body 10 of the push nipple at the ends 16 thereof, exclusive of the plastic coating 22. The diameter of the opening 30 in the boss is less than the diameter of the body 10 at its central thickest part between points 18. A clearance groove 34 is provided in each of the bosses 26 adjacent the opening 32, the'clearance grooves 34 connecting with flat faces 36 on the bosses 26. It should be noted that with respect to FIGURE 2 the actual amount of taper of the bore within the bosses is-exaggerated for clarity of illustration just as the outer curvature of the body It) is also exaggerated in'this figure, as well as in FIGURE 1, for the purpose of illustration.

In order to assemble a pair of sections to provide the assembly shown in FIGURE 2, the nipple has one end inserted in one of the bores in one section and then the other section is brought up to the exposed end of the nipple and the bore thereof placed over the nipple. All of the sections may be preassembled in this manner. Then pressure is applied to all of the sections to cause the nipples to be pushed home to the position shown in FIG- URE 2. Alternatively, two adjacent sections can be assembled and pushed home and then successive individual sections assembled individually and pushed home. It is also contemplated that the assembly may be expedited and that initial stabilization of the adhesive started by heating the sections just prior to assembly.

During assembly, the configuration and sizes of the tapered bores and push nipples are such that a substantial amount of the plastic 22 from the surface is displaced .into the clearance spaces 34 and between the faces 36.

Depending upon the relative sizes and the tolerances of the nipples and the bores, the clearance spaces 34 may be substantially completely filled or only partially filled, as shown in FIGURE 2. Radiator or boiler sections assembled as described herein need no additional tie bolts or other means to maintain them in assembled relationship with the control push nipples providing the total holding power to join the sections together.

Although the reasons for the superior holding power of the assembly. according to the present invention over uncoated push nipple assemblies with cast iron sections are not completely understood, it is believed that a combination of metal-to-metal contact and adhesive-to-metal contact with the adhesive filling the pores and voids or recesses of the adjacent metal surfaces, provides a strong interlocking bond of substantially greater strength than would be obtainable either with conventional metal-tometal contact alone or with a thick adhesive joining of the parts without forced together metal-to-metal contact.

In order to determine the characteristic of the bond between the push nipple and the bore of the sections, several radiator sections were joined together using a push nipple wtih adhesive on the surface thereof, as described previously, and sections were cut through the radiator at the joints and the cut section polished and examined microscopically at various powers of magnification from 50X to 25 OX This microscopic examination revealed that the interface between the push nipple and the surface 28 from the end of the bore 30 to location A shown in FIG- URE 2 was characterized in that usually the opposite metal surfaces were definitely spaced from each other with the plastic bridging the space between them with little or no metal-to-metal contact. The cast iron of the radiator section, to a greater extent, and the malleable iron of the push nipple, to a lesser extent, both had pits or pores or void areas which areas were filled with the plastic, the voids of the cast iron being filled by the plastic being displaced and forced therein during the joining operation. Likewise, the interface between the push-nipple 10 and the surface 28 from the end of the bore 32 to the point B, shown in FIGURE 2, were also normally definitely spaced from each other with similar bridging of the plastic and little or no metal-to-metal contact. Also, in this section pits and voids in both the cast iron and malleable iron were filled with the plastic. However, the interface between the points A and B, shown in FIGURE 2, showed regions which appeared to be of essentially metal contact between the outer surface of the body 10 of the push nipple and the surface 28, as well as regions where the metal surfaces were spaced and bridged over with the plastic. At these bridged-over or filled spaces the opposing metal surfaces also had areas or voids which the plastic filled. Some of the pits and voids which were directly opposite each other had the adhesive extending from inside one pit or void over to and inside the other pit or void. The boundaries of such pits and voids sometimes shows metal-to-metal contact and in other places a thin layer of adhesive between the opposite metal surfaces.

FIGURE 3 is a somewhat diagrammatic representation of a portion of the interface between points A and B as it appears under magnification of between about 50X and 250 showing areas of essentially metal-to-metal contact and areas of spaced walls bridged over by the adhesive. It was also noted that due to the variations within tolerances of the sizes of the tapers in the bosses 26 and the sizes within tolerances with the outer surfaces 14 of the body 10 that the distance between points A and B varied from joint to joint, and even varied on opposite sides of a single joint. In some cases the distance between points A and B was rather extensive, whereas in other cases it was a relatively small portion of the total area forming the joint. Usually, however, the distance from the surface 30 to point A was somewhat longer or more extensive than the distance from surface 32 to point B. It was also noted that during assembly the outer surface 14 of the body 10 would distort and assume generally the configuration of the tapered bore, particularly between the points A and B conforming to any irregularities or out of roundness of the bore. As indicated above, it is believed that a combination of this plastic adhesive flowing into the pits and voids of the adjacent metal surfaces, as well as the metal to-metal contact present, coupled with the compressive squeezing action of the radiator sections on the nipples, provides an extremely strong bond between the radiator sections and the push nipples which resists separation to such a degree that no additional tie bolts or locking means are needed to maintain the sections together. It is also believed that the adhesive flowing between the flat faces 36 of the bosses contribute to some minor extent to the greatly increased bond holding the sections together.

The increased holding power of sections joined by nipples of this invention was demonstrated by comparing the strength of sections joined by adhesive coated nipples according to this invention with sections joined with uncoated similar nipples of the prior art. The tests were performed by first joining several sections of radiators with uncoated push-nipples according to convention prior art practice, but omitting the use of tie bolts. The joined sections were then subjected to pressure. In all cases the joints failed before the burst pressure of the sections was reached and usually this was at a value less than the required rating of pressure to be withstood. Then similar sections were joined with push-nipples coated with adhesive according to this invention and subjected to pressure. In virtually all cases the required pressure rating was exceeded without joint failure and in many cases a radiator section Iburst while the joint continued to hold. These tests demonstrated the superior holding power of joints formed according to this invention with adhesive coated push-nipples.

An additional advantage of the plastic coating on the body of the push-nipple is the increased efiectiveness of the fluid seal between the push-nipple and the tapered bore even if used in conjunction with conventional tie bolts. The plastic around the nipple and between the interfaces of the metal provides an extremely good seal, the plastic flowing to all of the exposed areas to prevent fluid leakageto a much greater extent than can be achieved with uncoated nipples. In using prior art uncoated pushnipples for assembling sections, there always was a certain number of leaking joints caused by imperfections on the mating surfaces, out of tolerance surfaces, etc.; however, with the adhesive coated nipples of this invention, virtually no leaking joints have been encountered.

It is also contemplated that the plastic may be made of a material which is filled with finely divided metal particles and if the assembly is heated to a suflicient temperature to burn out the filler material, the metal particles remaining will be securely bonded together to provide a strength increasing seal.

Also, filler material can be added to the plastic to strengthen the plastic and/ or raise the temperature which it can attain without burning out or being degraded.

It is to be understood that the shape of the outer surface need not be limited to the exact configuration described, it only being necessary that it taper from a smaller diameter at its ends to a larger diameter at its middle, with the smaller diameter being smaller than the opening of the radiator boss and the larger diameter being larger than this opening 32 of the boss.

Having thus described the invention in an embodiment thereof, it is realized that numerous and extensive departures may be made from the method and apparatus described without departing from the scope of the invention as defined in the appended claim.

We claim:

Means for joining a pair of hollow cast iron members which members each have a passage communicating with the exterior and terminating in an opening and wherein the walls of said passages taper outwardly toward said Opening and wherein said passage has a smaller diameter Where it communicates with the exterior and a larger diameter at the opposite end thereof, comprising a malleable metal tubular member disposed within each of said passages to provide interconnection therebetween, said tubular member having an outer surface which curves from a smaller diameter at the ends thereof to a larger diameter at the central portion thereof, said tubular member having a portion of its outer diameter larger than a portion of the diameter of the opening, said outer surface of the tubular member having a coating thereon of a synthetic resin having the property of adhering to and bonding metals, said resin being resistant to deterioration at temperatures above 225 F., said outer surface of said malleable member having line contact at tangency with each of said passages which line contact expands to area contact on deformation, said expanding area of contact causing a portion of the resin to be forced into interstices between said Walls of the opening and the outer surfaces of said malleable member resulting in said area of contact having regions of essentially metal to metal contact and regions of resin interposed in the interstices between the metal surfaces, the opposing surfaces of said malleable member and said passages on both sides of said area of contact with each passage wall being essentially free of metal to metal contact and bridged by said resin, whereby a bond-seal is provided by said contact areas and a seal is provided by the bridging resin on each side thereof.

References Cited UNITED STATES PATENTS 2,180,960 11/1939 Kennedy 285284 X 2,409,283 10/ 1946 Hudson.

2,643,646 6/1953 Dunn 122-231 3,210,102 10/1965 Joslin 285-284 X 3,286,341 11/1966 Miller.

FOREIGN PATENTS 813 1/ 1905 Great Britain. 292,513 8/ 1953 Switzerland.

CARL W. TOMLIN, Primary Examiner. R. G. BERKLEY, Assistant Examiner.

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