Patent Application
20070251684
The present invention relates to a boiler and/or heat exchanger used in a domestic and/or commercial heating and/or hot water and/or steam system, and more specifically, the present invention relates to a watertube structure and to methods of making a watertube and assembling it within a boiler and/or similar heat exchanger.
Examples of boilers having watertubes are provided by U.S. Pat. No. 1,824,256 issued to Bryan and U.S. Pat. No. 4,993,368 issued to Jones et al. For example, the Bryan patent discloses a boiler having a plurality of bent watertubes extending through a combustion chamber. The ends of the bent watertubes connect to the upper and lower domes of the boiler via separately manufactured tapered fittings.
A conventional watertube for a boiler and/or heat exchanger is typically made of a metallic material and has substantially constant inner and outer diameters from end-to-end. The tubes extend in various bent, serpentine, or other shapes or patterns between opposite free ends. A separately-manufactured tapered fitting is typically welded to each free end to enable the tubes to be connected in a fluid-tight and secure manner to domes, manifolds, and like castings.
The separately-manufactured fitting typically provides the end of the tube with an outwardly-extending circumferential ring and a tapered end section. The tapered end section is inserted into a corresponding tapered hole, port or socket in a dome, manifold, or like casting. A clip, clasp or like fastener is typically applied to the circumferential ring to ensure that the inserted tube end remains in engagement with the dome, manifold, or like casting.
A 45° angle fillet weld is typically used to connect the fitting to the tube. The 45° angle fillet weld extends from an upper, exposed, radially-extending end surface of the circumferential ring to the adjacent outer wall surface of the tube. A problem with the use of the fillet weld is that the fillet weld eliminates any clean or flat surface of the circumferential flange on which a force can be readily applied to drive the tube end into the hole in a dome or the like. Existence of the fillet weld further complicates the already difficult and inefficient process of handling relatively heavy tubes within small spaces available during a boiler or heat exchanger assembly and the process of driving the tube ends into position within the boiler in a manner that provides leak-free connections.
Accordingly, there is a need for a watertube structure that can be handled and driven more easily into a hole, port or socket of a dome, manifold, or casting to create a leak-free connection therewith. In addition, there is a need for an efficient process of assembling watertubes in boilers and heat exchangers and for making watertubes.
According to a first aspect of the present invention, a method of making a tube for a boiler or heat exchanger is provided. A one-piece tube for use as a watertube within a boiler or heat exchanger has a free end section of a predetermined substantially-constant diameter. The method includes the step of forming an integral, outward-extending circumferential ring, or flange, on the free end section of the tube a spaced distance from an adjacent end face of the tube. This may be accomplished by radially expanding the tube within the free end section followed by axially compressing the free end section to cause a portion of the tube to bulge radially outward to form the circumferential ring or flange. The method can also include the step of forming the free end section of the tube that extends from the circumferential ring, or flange, to the adjacent end face of the tube with a taper such that the diameter of an outer wall of the tube progressively decreases from the circumferential ring, or flange, to the end face. Preferably, the tube is made of a metallic material and the forming process is cold or hot forming process.
According to another aspect of the present invention, a method of assembling a watertube boiler or heat exchanger is provided. A one-piece metallic tube having a free end section of a predetermined substantially-constant diameter is cold and/or hot-formed to produce an integral circumferential flange extending outwardly from the tube a spaced distance from an adjacent end face of the tube. A force is applied on a radially-extending surface of the circumferential flange to drive the end of the metallic tube into a hole, port or socket of a dome, manifold or like casting of a watertube boiler or heat exchanger to secure the one-piece tube to the dome, manifold or like casting. Before being engaged with the dome, manifold or like casting, the free end section of the metallic tube that extends from the circumferential flange to the adjacent end face can be formed with a taper such that the diameter of an outer wall of the tube progressively decreases from the circumferential flange to the end face.
According to yet another aspect of the present invention, a boiler or heat exchanger is provided. The boiler or heat exchanger has at least a pair of opposed domes, manifolds, or like castings and one or more metallic watertubes each having opposite ends connected to the opposed domes, manifolds, or like castings. At least one end section of the one-piece watertube is formed to have an integral outwardly-extending circumferential flange. The flange provides a readily-engagable, radially-extending surface on which a substantially axially-directed force can be applied to drive the end of the tube into sealing engagement with a hole, port, or socket of one of the domes, manifolds, or like castings. Preferably, a portion of the tube extending from the circumferential flange to an adjacent end face of the tube is formed with an inward taper such that a diameter of an outer wall of the tube progressively decreases from the circumferential flange to the end face. A wall defining the hole, port, or socket in the dome, manifold or like casting can be tapered to enable tight engagement with the tapered end of the tube. The watertube can have a substantially serpentine shape between its opposite ends.
The features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which:
The present invention relates to watertubes that are used in commercial boilers, heat exchangers, and like apparatus.
A typical watertube is made of a metallic material. The inner and outer diameters of such a watertube are typically constant from end-to-end. For example, the outer diameter of each tube may be 1.5 inch, and the inner diameter of each tube may be 1.25 inch thereby providing a tube wall thickness of about 0.125 inch. The watertubes can extend in serpentine or other shaped paths including linear shaped paths. The watertubes are assembled within boilers, heat exchangers and like apparatus.
A watertube 30 according to the present invention is similar to watertube 20 discussed above; however, the watertube 30 is provided as one-piece without the use of separately-manufactured fittings, nipples, or like coupling devices secured or welded thereto. Rather, the watertube 30 according to the present invention has a free end section that is formed into a desired shape without any component being added or welded thereto. Accordingly, there are no fillet welds or the like capable of providing leakage paths.
The method of making the watertube 30 is shown in
The die 38 shown in
After the end section 32 is expanded, an upsetting element 46 or the like engages the end face 36 and applies an axially directed force thereon to thereby compress the axial length of the end section 32. The upsetting element 46 can include an insertable support section (not shown) that extends within the end section 32 of the tube 30 while the upsetting element 46 applies the desired axial force. A face 48 of the holding clamp 34 has an annular recessed molding area 50 into which the end section 32 bulges in response to the axial compression. This results in the formation of an integral, radially outward extending, circumferential ring, or flange, 52. Preferably, the flange 52 includes a radially-extending, substantially-flat surface 54 that is located on a distal side of the flange 52 and that is readily engagable by a forked or like driving tool (not shown) for reasons discussed in greater detail below.
After the end section 32 is radially expanded and axially compressed, one or more dies 56 is utilized to provide the end section 32 with an outer diameter D2 that tapers inward from the flange 52 to the end face 36. For example, the die 56 can have a tapered inner surface 58 that is telescopically forced over the end section 32 to thereby radially contract the outer and inner diameters of the end section 32. In this way, the die 56, or a set of dies, can be used to provide the end section 32 with a frustoconical, or gradually tapered, outer wall 60.
As stated above, the tube 30 can be made of metallic material, for example steel. Of course, watertubes made of other materials can also be used. Preferably, the forming steps are cold and/or hot-forming steps without the use of any stress-relieving process steps, and both ends of the tube 30 can be formed as described above. Accordingly, the watertube 30 is a one-piece tube without separately-manufactured fittings or nipples and without welded connections.
The watertube 30 having a formed end section 32 as shown in
A forked tool (not shown) or the like is utilized to engage the unobstructed, radially extending surface 54 of the circumferential flange 52 and exert a substantially axially directed force thereon to efficiently drive the tapered end section 32 into the hole, port, or socket. Thereafter, a clip, clasp or like fastener can be placed over the flange 52 to ensure that it remains engaged with the dome, manifold or like casting.
The above described methods, boiler, heat exchanger and like apparatus provide watertubes that can be driven more efficiently and more easily into domes, manifolds and the like. The use of separate fittings and welds are eliminated thereby eliminating the possibility of weld leaks and the like. In addition, a driving force can be applied to the tube during the assembly process without concern of creating leakage paths. The end forming process also enables better control over tube tolerances with respect to diameters, tapers and the like to further ensure the formation of fluid-tight connections.
Various changes can be made to the above referenced methods and apparatus. For example, the circumferential flange 52 can be continuous or discontinuous, and the flange surface 54 can be of shapes other than substantially-flat. For example, the flange can be formed with a surface having a series of slots, recesses, or the like adapted to engage the head of a driving tool. One or both ends of the tube can have a formed end, and the tube can extend in a bent or linear path. The taper of the end section can be a gradually continuous uniform taper or a non-uniform varying taper. Alternatively, a uniform, non-tapered end section can be utilized.
While preferred methods and apparatus have been described in detail, various modifications, alterations, and changes may be made to the present invention without departing from the spirit and scope of the present invention as defined in the appended claims.
