US2763470A

US2763470A - Heat exchanger fin fastener

Info

Publication number: US2763470A
Application number: US492279A
Authority: US
Inventors: George M Certain
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-03-04
Filing date: 1955-03-04
Publication date: 1956-09-18
Anticipated expiration: 1973-09-18

Description

m N E w M A m RF @R m MA w GX E T A E H Set, 18. 1956 Filed March 4, 1955 NIH ATTORNEY HEAT EXCHANGER FIN FASTENER George M. Certain, Tulsayokla.

Application March 4,1955, Serial No. 492,279

6 Claims. (Cl. 257-262.2)

This invention relates to finned tubing for heat exchangers and consists more particularly in new and useful improvements in a method and device for securing helical fin strips to lengths of tubing for use in heat exchanger units.

Inthefieldof heat exchangers, there are many forms of finned tubing in which a length of tubing ishelically wound with a strip of heat radiating material. In the fabrication of some of these heat exchange elements, it is customary to form the fin by winding a continuous straight strip or ribbon of metal into a Hat 'helical coil which is subsequently secured around its inner edge to the surface of the tube, by soldering. In others, the tube is fed and rotated in such a manner that a strip of thin metal will be wound around the tube and secured thereon, all in one operation. In this form the fin strip is usually formed in such a manner as to provide a securing edge by means of which it can be secured to the tube by solder or the like.

In the past, most of the finned tubing of this type has been formed with copper fins with which the operation of soldering has presented no great difficulty. However, more recently methods have been developed for helically winding aluminum strips on brass tubes and as aluminum is more difficult to solder than other metals previously used, means have been devised to swedge the inner edges of the helical strips on to the brass tubes and although this system has been satisfactory in binding the major area of the helical fin to the brass tube, it is still necessary to solder or otherwise secure the extremities of the helical fin to the tube sections before the finned tubing is installed in a heat exchanger unit. Otherwise, it has been found that the extremities of the helical fin have a tendency to dislodge which tends to weaken the entire structure under the influence of vibration.

Even this minimum soldering operation has caused considerable difficulty when aluminum strip is used for forming the helical fin, because of the fact that special aluminum solder is required and experience has shown that this deteriorates very rapidly under service conditions.

It is therefore, the principal object of the present invention to overcome this difficulty by providing a specially designed fin fastening device which may be formed of copper wire or other suitable metal wire adapted to be soldered to the supporting tube with conventional tinlead solder and mechanically connected to the convolutions of the helical fin at the extremities thereof, to firmly secure the fin in place on the tube.

A further object of the invention is to provide an auxiliary fastening device for the extremities of helical fins which have been swedged on to a supporting tube, said fastening device being secured to the tube with ordinary tin'lead solder and an organic flux which when applied will last for the life of the tube.

With the above and other objects in view which will appear as the description proceeds, the invention consists ited States Patent M 2,763,470 Patented Sept. 18, 1956 in the novel features herein set forth, illustrated in the accompanying drawings and more particularly pointed out in the appended claims.

Referring to the drawings in which numerals of like character designate similar parts throughout the several views,

Figure 1 is a side elevational view of a heat exchanger tube, broken away, showing the fin fastening devices applied to opposite extremities of the tube.

Figure 2 is an end elevational of the same.

Figure 3 is a top plan view of one end of a heat exchanger tube, showing one form of fin fastener, and

Figure 4 is a similar view of another tformof fastener which in practice, is the preferred form.

In the drawings, referring first to Figure 1, a section of heat exchanger tubing is generally represented by the numeral 6 and consists of a core 7 formed in this'instance of a length of brass tubing. Surrounding this tube substantially from end to end, is a helical fin 8, formed of a continuous strip of aluminum wound spirally on the tube. Preferably, the strip 8 is formed with a base flange or foot 9, bent angularly so as to embrace the periphery of the tube 7 and swedged thereon during the "winding process.

As previously stated, when aluminum strip is used for the heat exchanger fin, a special aluminum solder is required if the fin is to be secured to the tube by soldering. This naturally reduces the lifeof the fin tube, due to the inability of aluminum solder to stand up under operating conditions. However, by providing this angular base flange 9'on the fin and swedging it on to the tube, the fin is firmly secured from end to end, without the need of solder or other securing means, so long as there are no strains on the extremities of the helical fin to initiate separation. Such initial separation of the end convolutions of the fin can be caused during shipment of the tin tube sections or when they are installed in heat exchanger units, due to vibration during operation.

"It is to meet this requirement that the present invention provides an auxiliary fin securing device, generally indicated by the numeral 10, for securing opposite extremities of the fin to the tube. This device is preferably composed of a length of copper wire, one end of which is formed into a ring or loop 11, of a diameter to fit over the periphery of the tube 7 with a sliding clearance. The opposite end of the wire provides a fin engaging member which is bent radially outwardly from the ring 11 as at 12, and in the simplest embodiment, shown in Figures 1 and 3, terminates in a right angular projection 13, lying parallel with the axis of the tube 7.

The method of applying these fastening devices comprises first, drilling a series of aligned holes 14 through a predetermined number of successive helixes of the fin strip 8 from each extremity of the fabricated fin tube 6. A fastening device 10 is then applied at each end of the tube by slipping rings 11 over the respective ends of tube 7 and inserting their angular projections 13 through the aligned holes 14 as shown in Figure 3. The rings 11 after being brought into juxtaposition to the extreme outer helixes at each end of the tube, are soldered to the tube with regular tin-lead solder and an organic flux, by conventional means. Thus, with the rings 11 permanently fixed to the tube 7 and the projections 13 mechanically engaging the fin strip at each end of the tube, the fin is secured against radial or peripheral displacement with respect to the tube, to maintain the rigid engagement of the fin with the periphery of the tube.

In the preferred embodiment of the invention shown in Figure 4, the projection 13a is in the form of a hook which engages a hole 14 in at least one helix at each end of the tube. The projections 13a are inserted in the respective holes 14 and then bent over against the inner surfaces of the fin strip. Otherwise, the fastening device and method of application are the same as previously described.

Thus, with both forms of the invention illustrated, it will be seen that by firmly anchoring the ring of the fastening device to the periphery of the tube and mechanically connecting the other end of the device to one or more helixes of the fin strip, any movement of the end helix which might otherwise initiate displacement of the base of the fin, is prevented. Furthermore, by the use of tin-lead solder the anchoring of the fastening rings to the periphery of the tube is permanent and the auxiliary fastening device remains effective throughout the life of the equipment.

It should also be noted that the very simplicity of this invention and the ease with which it may be applied, greatly facilitates the fabrication of finned tube sections for heat exchanger units.

- From the foregoing it is believed that the invention may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details of construction without departing from the spirit of the invention as set forth in the following claims.

I claim:

1. In a finned tube for heat exchangers, including a tubular core and a fin strip helically wound thereon with its inner edge from end to end, continuously secured to the periphery of said core and its outer edge projecting radially from the core; an auxiliary fastening device for the opposite extremities of said strip, each comprising an anchoring member rigidly connected to the periphery of the core, a connecting member integral with said anchoring member, offset radially from the periphery of said core and terminating in a projection which transversely penetrates at least one helix of said fin strip.

2. In a finned tube for heat exchangers, including a tubular core and a fin strip helically wound thereon with its inner edge from end to end, continuously secured to the periphery of said core and its outer edge projecting radially from the core; an auxiliary fastening device for the opposite extremities of said strip, each comprising an anchoring ring embracing the periphery of said core, a connecting member integral with said ring, oflset radially from the periphery of said core and terminating in a projection which transversely penetrates at least one helix of said fin strip.

3. In a fin tube for heat exchangers, including a tubular core and a fin strip helically Wound thereon with its inner edge from end to end, continuously secured to the periphery of said core and its outer edge projecting radially from the core; an auxiliary fastening device for the opposite extremities of said strip, each fastening device being formed of copper wire and comprising an anchoring ring adapted to be soldered to the periphery of said tube, a connecting member integral with said ring, offset radially from the periphery of said core and terminating in a projection which transversely penetrates at least one helix of said fin strip.

4. In a fin tube for heat exchangers, including a core formed of a brass tube and a fin strip of aluminum, helically wound thereon with its inner edge from end to end, continuously swedged to the periphery of said brass tube and its outer edge projecting radially from said tube; an auxiliary fastening device for the opposite extremities of said strip, each fastening device being formed of copper wire and composing an anchoring ring adapted to embrace the periphery of said tube and soldered thereto, a connecting member integral with said ring, offset radially from the periphery of said tube and terminating in a projection which transversely penetrates at least one helix of said fin strip.

5. In a fin tube for heat exchangers as claimed in claim 4, wherein said projection comprises a straight finger penetrating a series of helixes and lying in a plane parallel to the axis of the tube.

6. In a fin tube for heat exchangers, as claimed in claim 4-, wherein said projection comprises a hook shaped member which projects through at least one helix at each end of the tube and is bent angularly to embrace the opposite face of the helix.

References Cited in the file of this patent UNITED STATES PATENTS 1,972,230 Lehman Sept. 4, 1934