US3355788A - A method of sawing slits in finned tubing - Google Patents

A method of sawing slits in finned tubing Download PDF

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Publication number
US3355788A
US3355788A US405143A US40514364A US3355788A US 3355788 A US3355788 A US 3355788A US 405143 A US405143 A US 405143A US 40514364 A US40514364 A US 40514364A US 3355788 A US3355788 A US 3355788A
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Prior art keywords
tubing
fins
saw
slits
saws
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US405143A
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Addison Y Gunter
Thomas E Owen
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Hudson Engineering Corp
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Hudson Engineering Corp
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Priority to US405143A priority Critical patent/US3355788A/en
Priority to GB38244/67A priority patent/GB1101812A/en
Priority to GB4726/65A priority patent/GB1101811A/en
Priority to FR6733A priority patent/FR1431159A/fr
Priority to BE660122D priority patent/BE660122A/xx
Priority to DE1776242A priority patent/DE1776242C3/de
Priority to DE1965H0055694 priority patent/DE1452313A1/de
Priority to NL656508074A priority patent/NL141411B/xx
Application granted granted Critical
Publication of US3355788A publication Critical patent/US3355788A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D53/00—Making other particular articles
    • B21D53/02—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers
    • B21D53/08—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers of both metal tubes and sheet metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
    • B21C37/15—Making tubes of special shape; Making tube fittings
    • B21C37/22—Making finned or ribbed tubes by fixing strip or like material to tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23C—MILLING
    • B23C3/00—Milling particular work; Special milling operations; Machines therefor
    • B23C3/28—Grooving workpieces
    • B23C3/30—Milling straight grooves, e.g. keyways
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
    • B23D45/00—Sawing machines or sawing devices with circular saw blades or with friction saw discs
    • B23D45/12—Sawing machines or sawing devices with circular saw blades or with friction saw discs with a circular saw blade for cutting tubes
    • B23D45/122—Sawing machines or sawing devices with circular saw blades or with friction saw discs with a circular saw blade for cutting tubes for cutting slots in tubes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S83/00—Cutting
    • Y10S83/929—Particular nature of work or product
    • Y10S83/952—Moving work
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4935—Heat exchanger or boiler making
    • Y10T29/49377—Tube with heat transfer means
    • Y10T29/49378—Finned tube
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T83/00—Cutting
    • Y10T83/02—Other than completely through work thickness
    • Y10T83/0304—Grooving
    • Y10T83/0311—By use of plural independent rotary blades

Definitions

  • This invention relates to the manufacture of finned tubing for heat exchange use, and includes an improved finned tube, a process and machine for the production thereof.
  • fins made of metal having a high coefiicient of heat transfer have been formed on heat exchange tubing as separate discrete cross fins, or as a single continuous strip of metal on the tube in helical configuration and attached by various means. Fins have been held by embedding in a groove in the exterior of the tubing, attached by welding or soldering, brazing, or flanged at the point of contact of the fin and tubing and held firmly on the tubing by tension applied in winding or extruding the fin.
  • slots or openings in the fins greatly increase the eificiency of heat transfer, especially when the fluid flowing across the outside of the tubing is a gas. This increase in efficiency is regarded as due to increased turbulence and reduction of laminar film of fluid in contact with the fin. Louvered type openings designed to increase turbulence are shown and described by Buschow in U.S. Patent 2,643,863 and fins having slots in their peripheries are shown by Rodeck in US. Patent No. 2,372,795.
  • a fin of definite thickness conducts heat substantially in proportion to its surface area, so that formation of openings and slits in such fins reduces the rate of flow of heat through the fins, although the improvement in heat transfer resulting from turbulence and reduction in laminar film structure of a fluid flowing across the fins is great enough that it outweighs the losses due to decreased surface area of the fins.
  • the fins are so flexible that impact of saw teeth flatten the fins along the central tube beyond the limit of elasticity of the fins so that they do not recover their position substantially vertical to the longitudinal axis of the tube;
  • saw teeth do not bite into the fins properly, so that slits when formed by saws are worn into the fins rather than cleanly cut and as a result the slits have many long hair-like threads of metal, or whiskers, adhering in the slits which greatly increase pressure drop in a heat exchanger provided with such finned tubing, and
  • saws although made of very hard steel wear out so quickly, even when fins of soft aluminum are, cut, as to make the process impractical.
  • fins must be supported in a matrix of wax, or the like, if they are to be slit by sawing, and no one, to our knowledge, has been able to saw clean radial slits in such fins without production of excessive numbers of adhering threads of metal, or flattening the fins excessively.
  • Another object is to provide a machine and process for sawing substantially radial slits in fins on finned tubing and twisting fin sections between the resulting slits into louvered or herringbone configuration.
  • Another object is to provide a machine and process for sawing slits in fins of finned tubing in which production of excessive numbers of threads or whiskers of metal adhering to the fins adjacent to the slits is prevented.
  • Another object is to provide a method and machine for sawing slits in fins of finned tubing in which maximum surface area of the fins is retained.
  • Another object is to provide an improved method and machine for sawing slits in fins on finned tubing in which saw teeth wear well.
  • Another object is to provide a process of the above type in which linear speed of finned tubing and saw tooth cut per impact are correlated to cut clean slits in fins supported only by the tubing.
  • Still another object is to provide a machine and method for sawing slits in fins on finned tubing at high rates of speed and at low labor costs.
  • Another object is to provide improved finned tubing for heat exchanger use in which fins on the tubing have approximately radial slits with substantially parallel sides extending from the periphery of the fins toward the tubing.
  • Another object is to provide such finned tubing having sections of fins defined by adjacent slits twisted into louvered or herringbone configuration.
  • Another object is to provide improved finned tubing for heat exchanger use which results in a large increase in heat transfer rate.
  • Another object is to provide improved finned tubing for heat exchanger use which does not cause excessive pressure drop in a heat exchanger equipped with such tubes.
  • finned tubing having fins extending outward of the exterior of the tubing and supported only by the tubing is passed in axial direction through an assembly of saws; and slits extending approximately radially from the periphery of the fins toward the tubing are sawed into the fins.
  • the slits may be at an angle of as much as 20 from the radius if desired.
  • fins is used in this specification and claims to include consecutive turns of helical fins, or discrete fins, applied and attached to the tubing in any manner, since the process applies equally to fins of any cross-fin type.
  • the number of saws in the assembly is equal to the number of radial slits desired in a finished fin and the saws are arranged at equal angular distances from each other around the circumference of the tubing, but the number of saws may be a fraction of the desired number of slits and the tubing may be passed through the saw assembly, turned through suitable circumferential arc, and passed through the saw assembly again until a series of slits of desired number and spacing in the circumference of the fins is obtained.
  • the saws are preferably of flat circular type, having widely spaced teeth on the blades. While other types of saws, as for example, band saws, can be used, these are more expensive than simple circular saws and are inconvenient to arrange in a saw assembly of reasonable length, so that the circular saws are much to be preferred.
  • the linear rate of travel of the finned tubing through the saw assembly and speed of the saws are controlled so that each saw tooth cuts small chips of metal cleanly from the fin without production of an. excessive number of threads or whiskers of metal adhering to the fins at the edges of the slits.
  • control of the ratio of linear speed of the finned tube through the sawing zone to the speed of the saws within certain limits results in avoiding production of such threads or whiskers of metal, prevents excessive wear on saw teeth, and prevents deformation and flattening the fins to an undesirable extent.
  • the sections of fins bordering each slit are twisted so that these sections of fins converge, with the sections bordering alternate slits converging toward the leading and trailing ends of the finned'tubing, thus giving the fin a herringbone configuration.
  • the slits are sawed into the fins to a depth of'a'bo'ut 0.3 to 0.7 of the total height of the fin.
  • the machine of'our invention includes a saw assembly in which a plurality of circular saws having widely spaced teeth are arranged in planes defined by radii and the longitudinal axis of finned tubing to be passed through the assembly.
  • the saws are located in these planes so that each tooth of each saw contacts a plurality of fins on the 'fin'nned tubing successively during a single revolution of a saw blade.
  • Means are provided for driving all saws at selected speeds which may be difierent for saws cutting uphill and downhill if desired and feed means for finned tubing is arranged to pass finned tubing through the saw assembly at a selected linear speed.
  • the feed means also provides continuous orientation of the tubing withrespect to the saw blades so that the tubing does not rotate on its axis as it passes through the saws, although the tubing may rotate a few degrees in passing through the saw assembly without loss of advantages.
  • Means for adjustably selecting either the saw speed or linear speed of the tubing or both is provided, so that a selected ratio ofsaw speed to linear speed of tubing may be maintained. It is not necessary that all saws run at the same speed. So long as the ratios of saw speed to tubing speed provide an average saw tooth bite or cut per impact within themaximum and minimum values described below, any or all the saws may be operated at any speed desired.
  • the means for driving the saw blades may be arranged so that the saw blades of alternate saws rotate in opposite direction.
  • a means for twisting the sections left between adjacent slits into such converging or herringbone patterri is provided.
  • This means preferably is a ring having inward projecting fingers or pins disposed to enter alternate slits in 'the periphery of the fins, and contact the fin sections on at least one side of the corresponding slit so as to twist these sections .into positions converging toward the trailing end of the finned tubing.
  • This ring is preferably located at the exit of the saw assembly.
  • FIGHI is a schematic elevation of one preferred type of the machine of the present invention showing diagrammatically a saw assembly with cooperable feed and withdrawal apparatus for finned tubing;
  • FIG. 2 is an enlarged view of the completed finned tubing manufactured with the device of FIG. 1;
  • FIG. 3 is a plan view of a modification of the device of FIG. 1 illustrating alternative feed means
  • FIG. 4 is a vertical section through one unit of the saw assembly illustrating one preferred arrangement of saws therein;
  • FIG. 5 is a detail illustrating the arrangement of one pair of saws in the unit of FIG. 4;
  • FIG. 6 illustrates one means for twisting fin sections between slits to converge alternately toward leading and trailing ends of the finned tubing
  • FIG. 7 illustrates finned tubing emerging from the device of FIG. 6 with the fins twisted into herringbone configuration
  • FIG. 8 illustrates one preferred type of finned tubing suitable for feed into the machine illustrated in the remaining drawings.
  • the reference numeral 1 designates generally a feed section of the machine by which a length of finned tubing 2 is passed into a saw assembly designated generally as 3.
  • the assembly 3 is made up of a plurality of units illustrated as units 4, '5, 6, '7, 8 and 9 whose construction is illustrated in greater detail in FIG. 4.
  • a receiving section designated generally as 11 is disposed at the end of the saw assembly opposite to feed section 1.
  • both the feed and withdrawal apparatus are driven by a single unitary drive system designated generally as 12.
  • This drive section includes a motor 13 arranged to be driven at a selected constant speed controlled by any suitable speed control device illustrated as a rheostat 14.
  • Motor 13 is arranged to drive a master pulley 15 either directly or through a suitable train of gearingor other drive means (not shown).
  • Master pulley 15 through suitable drive means illustrated as belts 16 and 16a is arranged to drive pulleys 1-7 and 17a in the feed and Withdrawal sections of the machine respectively at the same speed.
  • the pulley 18 is disposed to drive a conveyor 21 illustrated as 'of belt type, which may be as long as required to carry a length of finned tubing in axial direction toward the saw assembly 3.
  • the feed section of the machine includes means providing continuous orientation of the tubing with respect to the saw blades illustrated as a pair of opposed belts 22 and 23 located at such distance from each other as to impose alight pressure upon the periphery of fins on tubing 2. This pressure is insufficient to bend the fins but is great enough to prevent the tube from rotating around its axis to any substantial extent while passing through the saw section.
  • Belt 22 is carried on driven roller 19 and idler rollers 24, 25 and 26.
  • Belt 23 may be carried entirely upon idler rollers as illustrated, arranged to give the belt the same general mirror-image conformation as belt 23.
  • Belts 27 and 28 in the withdrawal section of the machine are similar in construction to belts 22 and '23 and serve to prevent rotation of the tube about its longitudinal axis after the trailing end of the tube passes through belts 22 and 23.
  • Driven pulley 18a in the withdrawal section drives a conveyor 29 to carry the tubing to a suitable location for storage for further processing or use after passing through the machine.
  • a means for twisting sections of the fins defined by adjacent slots is illustrated at 31.
  • This means preferably is a ring 31 having fingers or pins 32 arranged to contact at least one side of the slit, and disposed to enter -every other slit in the periphery of the fins as the tubing passes through the ring.
  • These pins preferably have a diameter greater than the width of the slits and cause adjacent sections of the fin on opposite sides of each slit into which a pin 32 enters to be twisted sothat the edges of these sections of fin converge in a direction toward the trailing end of the tubing. Pins of lesser width which contact a fin section on only one side of the slit may be used if desired.
  • This twisting effect causes the edges of the fin sections at the slits between pins to be twisted in opposite directions so that the fin sections along these slitsconverge in the direction of the leading end of the tubing, thus giving the fins a herringbone configuration illustrated in FIG. 2.
  • FIG. 4 One preferred arrangement of saws in each unit of the saw assembly is illustrated in FIG. 4.
  • the entire unit designated generally as 4 includes a housing 341 preferably of cylindrical construction to save machine space, butwhich may have any outer shape desired, mounted on a means 35 for rotation through an arc, and carried on a support 36.
  • a plurality of saws illustrated as four saws, arranged in opposed pairs are carried on suitable bases 28 supported by a heavy center wall 37.
  • Motors 41, 42, 43 and 44 each have a shaft 45 carrying a circular saw blade 46 having teeth-4'7 'widely spaced from each other, and illustrated as 180 apart.
  • FIG. 5 The arrangement of saws in'opposed pairs is best shown in FIG. 5.
  • a series of aligned openings 48, 49 and 50 extend through the 'end wall of housing 34 and the heavy center wall 37 so that finned tubing may be introduced through the openings in position for the fins to be cut by the saw blades.
  • each unit the saws are illustrated as arranged in alternate pairs cutting at a right angle to each other.
  • FIG. 1 shows six consecutive units of saws although any number desired may be used. We have found that six units of four saws each cutting 24 slits at an angular 5 distance of from each other are preferred when one inch tubing'having %-inch fins thereon is to be processed,
  • Each saw ineachunit of the saw assembly is centered at a distance from the tubing and has such diameter that each'tooth on the saw blade contacts a plurality of fins,
  • FIG. .8 wherein the arc 59 illustrates the path of travel ofa sawtooth. It will be seen that when a saw located in'this manner rotates in clockwise manner that the tooth will approach tube 2 as it passes through the are 59 and conversely when the saw rotates in counterclockwise manner, the tooth will move further away from tube 2 I in arc 59 as succeeding fins are contacted by the tooth.
  • cutting with a saw tooth approaching the tube will be referred toas downhill sawing and cutting with a saw tooth .
  • a V-shape trough 61 adapted to guide finned tubing 2a into unit 4 of the saw assembly 3.
  • a tool tube holder 62 having an opening suitable to receive an end of tubing 2a is mounted for reciprocating movement in trough 61. This holder 62 fits the trough 61 so that the tubing cannot rotate about its longitudinal axis as it is moved into the saw assembly.
  • the tube holder is attached to the sliding block 63 which is drawn toward the saw assembly 3 by a flexible co'rd or cable 64 attached thereto and passing around pulleys 65, 66 and 67 to a drum driven through a worm and gear assembly 68, pulley 69, belt 70 and a variable speed motor 71.
  • This device is equally effective with that shown in FIG. 1 but is not quite so convenient in operation sinceit requires attachment of the end of the tube to the holding device 62 and detachment therefrom when the holder 62 reaches its extreme limit of travel.
  • tubing having continuous fins thereon is placed upon the feed means and is passed in axial direction through the saw assembly while the ratio of linear speed of the finned tubing to saw speed is controlled within certain limits to prevent excessive wear on the saw blades, flattening of the fins, and production of the sufficient number of adhering threads of metal to the fins at the edges of the slits cut to cause objectionable pressure drop across a heat exchanger fitted with such tubing.
  • the stiffness of the fins and'saw blade impact force are the basic factors deter-mining satisfactory ratios of linear speed of the finned tubing to saw speed. Stiffness of the fins is a complex function of fin height, fin thickness, type of attachment of fins to the tube, metallurgy of the fins and the depth of the radial slits to be cut into the fins. However, once the type, metallurgy and dimensions of the fins to be used and the depth of the cut are selected, the stiffness of the fins becomes a constant quantity and it need be considered only when a change is to be made to fins of different type.
  • Saw blade impact force is dependent on the thickness and speed of the saw and the depth of saw tooth bite or cut per impact in inches.
  • a B X C wherein M is the average saw tooth bite or cut per impact, A is the linear speed of the finned tubing in inches per minute, B is the number of fins per inch on the finned tubing, C is the total depth of the slit to be cut in inches, X is the revolutions per minute of a. circular saw, Y is the number of saw teeth on the blade, and Z is the number of fins contacted per tooth in a single revolution of the blade.
  • Tbistubing has an external. diameter of one inch and has eight helical turns of extruded aluminum fin per linear inch, each fin having a height of /8 inch and a thickness of 0.016 inch. In determining this value adjacent saws in the assembly were driven at the same rate of speed and in opposite directions, for a reason more fully explained below.
  • the saws used had a thickness of inch and had eight teeth located 45 aparton the circumference of the blade; and were arranged so that each tooth contacted seven fins successively in one revolution of the saw. Radial slits were cut into all fins to a depth of /4 inch.
  • a fin of the same type /2-inch high is somewhat stiffer than the /;-inch fin and the tooth bite or cut per impact may be increased to a value of 10 to 15 percent above 7 the value for a %-inch fin.
  • a %-lI1Ch high fin is not so stiff as the As-inch fin and the maximum tooth bite or cut per impact is correspondingly less.
  • Equation 1 Sf M wherein Sf is the stiffness of any thin fin and S Al is the stiffness of the /s-inch aluminum fins described above.
  • the diameter of the saw blade will affect the number of fins contacted by each saw tooth in a single revolution. We have found that 3 /2- to 4-inch diameter blades arranged to impact seven consecutive fins per revolution were best adapted to sufliciently compact arrangement as to avoid wasting machine space.
  • the minimum value for M in the above Equation 1 differs for uphill and downhill cutting.
  • the minimum average tooth bite or cut per impact is about 0.006 inch for downhill cutting using the /s-inch fins described above and is about 0.003 inch for uphill cutting.
  • the maximum value of M will be 0.02 inch for the %-inch fins and the minimum value will be about 0.006, since both uphill and downhill cutting will be used.
  • a ratio of saw speed to linear speed to the finned tubing is selected so that the value of M is between the maximum and minimum values permissible. "Either thesaw speed, tubing speed or both may then be adjusted to give the maximum rate of production without excessive flattening of the fins, without an excessive number of adhering threads of metal and without a high degree of saw wear.
  • the unsupported fins are cut cleanly, producing slits having substantially parallel sides extending from the periphery of the fins toward the tubing to a desired depth, thus leaving a greater area of fin than is present if the fin stock should be slitted along one edge prior to winding it on the tubing.
  • the latter type of operation inherently will give a triangular slot rather than a slit having substantially parallel sides. Twisting the fin section defined by two adjacent slits so that these sections alternately converge toward the leading and trailing ends of the tubing results in finned tubing which has an unusually high rate of heat transfer.
  • the critical factor in determining when flattening of fin sections and/or number of threads of metal adhering to the fins at edges of the slits becomes excessive is the ratio of percent increase in heat transfer rate to percent increase in pressure drop in fluid flowing across the-outside of the tubing when the improved finned tubing of the present invention is substituted in a heat exchanger for tubing of the same size and equipped with plain fins of the same diameter. Either flattening the fin sections from a position substantially perpendicular to the tubing, or the presence of threads of metal, or both, will increase the resistance to flow of fluid over the tubing and result in increased pressure drop in the heat exchanger.
  • A% Ht is the percent increase in heat transfer rate and A%P is the percent increase in pressure drop have a value of 2:1 or more, that is for example, if the heat transfer rate be increased by 50%, the pressure drop should not increase more than about 25%. However. under some circumstances greater increases in pressure drop can be tolerated but the minimum value of the ratio should not be less than 0.5:1. Therefore, the "terms excessive and excessively are used in this specification and claims in a special limited sense in connection with the terms flatten and flattening fin-sections, and number of adhering threads of metal and similar expressions to mean a quantity in excess of that required to reduce the value of the above ratio to 0.521.
  • the heat transfer rate in the above ratio is calculated in conventional manner asthe number of B.t.u. transferred per hour per square foot of heat transfer area per degree Fahrenheit in temperature difference. The pressure drop is stated in pounds per square inch.
  • a process for slitting finned tubing which comprises the steps of passing finned tubing in an axial direction through an assembly of rotary saws, said tubing having a series of extruded aluminum fins %-inch wide and 0.016 inch thick thereon supported only by the tubing; and therein sawing slits in each fin by controlling the speed of movement of the saws relative to speed of movement of the tubing to provide an average saw tooth cut per impact in the range from 0.02 inch to 0.003 inch according to the following equation:
  • M is the saw tooth cut per impact in inches
  • A is the linear speed of the finned tubing in inches per minute
  • B is the number of fins per inch of tubing
  • C is the total depth in inches of slits to be cut
  • X is the revolutions per minute of a rotary saw
  • Y is the number of saw teeth on the saw blade
  • Z is the number of fins contacted per tooth in a single revolution of the saw.
  • a method of manufacturing slitted finned tubing comprising the steps of moving tubing having thin cross fins supported only by the tubing in an axial direction, providing an assembly of circumferentially spaced apart, rotary type saws disposed in and parallel to the path of the fins of the tubing and having teeth thereon adapted, upon rotation of the saws, to move uphill or downhill with respect to the tubing during each pass through the fins, and rotating the saws at a speed relative to the speed of movement of the tubing to provide an average tooth cut per impact in the range from about Sf S f 0.003 inch 757- ⁇ ?” to 0.02 inch m wherein S1 is the stiffness of the fin, and S Al is the stiffness of an extruded aluminium fin %-inCh wide and 0.016 inch thick on a 1 inch outside diameter tube.
  • a method as defined in claim 3 including the step of twisting at least some of the sections of the fins defining adjacent slits so as to cause such sections to converge alternately toward the leading and trailing ends of the tubing.
  • a method of manufacturing slitted finned tubing comprising the steps of moving tubing having thin cross fins supported only by the tubing in an axial direction, providing an assembly of circumferentially spaced apart, rotary type saws disposed in and parallel to the path of the fins of the tubing and having widely spaced apart teeth thereon adapted, upon rotation of the saws to move uphill or downhill with respect to the tubing during each pass through the fins, rotating the saws at a speed relative to the speed of movement of the tubing which causes the saw teeth to slit each fin by cutting chips therefrom, and twisting at least some of the sections of the fins defining adjacent slits, so as to cause such sections to converge alternately toward the leading and trailing ends of the tubing, so that the resulting slitted finned tubing, when substituted in a heat exchanger for tubing of the same size and having plain fins of the same diameter, has a ratio of percent increase in heat transfer rate to percent increase in pressure drop in fluid flowing across
  • a method of manufacturing slitted finned tubing comprising the steps of moving tubing having cross fins formed of a metal having a high coefiicient of heat transfer and a thickness not substantially greater than 0.016 and supported only by the tubing in an axial direction, providing an assembly of circumferentially spaced apart, rotary type saws disposed in and parallel to the path of the fins of the tubing and having widely spaced apart teeth thereon adapted, upon rotation of the saws, to move uphill or downhill with respect to the tubing during each pass through the fins, rotating the saws at a speed which causes the saw teeth to slit the fins by cutting chips there from, and twisting at least some of the sections of the fins defining adjacent slits so as to cause such sections to converge alternately toward the leading and trailing ends of the tubing.
  • a method of manufacturing slitted finned tubing comprising the steps of providing an assembly of circumferentially spaced apart saws, moving tubing having thin cross fins supported only by the tubing through the assernbly so as to saw slits in the peripheries of the fins, and twisting at least some of the sections of the fins which define adjacent slits, during such movement of the tubing, so as to cause said sections to converge alternately toward the leading and trailing ends of the tubing.
  • a method of manufacturing slitted finned tubing comprising the steps of providing an assembly of circumferentially spaced apart rotary saws, moving tubing having thin cross fins supported only by the tubing through the assembly, and rotating some saws in a direction to saw slits in the fins as they move uphill therethrough and other saws in the opposite direction to saw slits in the fins as they move downhill therethrough, said saws being operated to twist the fins contacted in a direction corresponding to the movement of the contacting saw.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sawing (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
US405143A 1964-10-20 1964-10-20 A method of sawing slits in finned tubing Expired - Lifetime US3355788A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US405143A US3355788A (en) 1964-10-20 1964-10-20 A method of sawing slits in finned tubing
GB4726/65A GB1101811A (en) 1964-10-20 1965-02-03 Method for manufacturing slitted finned tubing for heat exchangers
GB38244/67A GB1101812A (en) 1964-10-20 1965-02-03 Apparatus for producing slitted-finned tubing
BE660122D BE660122A (de) 1964-10-20 1965-02-23
FR6733A FR1431159A (fr) 1964-10-20 1965-02-23 Tuyauteries à ailettes pour échangeurs de chaleur, et procédé et machine pour leur fabrication
DE1776242A DE1776242C3 (de) 1964-10-20 1965-04-02 Verfahren zur Herstellung eines Wärmeaustauschrohres sowie Vorrichtung zur Durchführung des Verfahrens
DE1965H0055694 DE1452313A1 (de) 1964-10-20 1965-04-02 Verfahren zum Anbringen von in Umfangsrichtung dicht benachbarten Schlitzen in Lamellen von Rohren fuer Waermeaustauscher
NL656508074A NL141411B (nl) 1964-10-20 1965-06-23 Werkwijze en machine voor het zagen van sleuven in de ribben van ribbenbuizen, alsmede ribbenbuis vervaardigd volgens deze werkwijze.

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Application Number Priority Date Filing Date Title
US405143A US3355788A (en) 1964-10-20 1964-10-20 A method of sawing slits in finned tubing

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US3355788A true US3355788A (en) 1967-12-05

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US405143A Expired - Lifetime US3355788A (en) 1964-10-20 1964-10-20 A method of sawing slits in finned tubing

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US (1) US3355788A (de)
BE (1) BE660122A (de)
DE (2) DE1776242C3 (de)
FR (1) FR1431159A (de)
GB (2) GB1101811A (de)
NL (1) NL141411B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3517576A (en) * 1965-03-24 1970-06-30 Gulf Research Development Co Cutting process
CN111215697A (zh) * 2020-03-02 2020-06-02 李远超 一种间距可调的分条设备
CN114769697A (zh) * 2022-06-15 2022-07-22 江苏辅星电子有限公司 一种铜散热片用的生产系统及制备方法
CN114769688A (zh) * 2022-04-29 2022-07-22 沈阳飞机工业（集团）有限公司 加工薄耳片深槽口的方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115990686A (zh) * 2023-03-22 2023-04-21 江苏巨弘捆带制造有限公司 一种用于钢带剪切分条过程的处理装置
CN116213825A (zh) * 2023-03-22 2023-06-06 未来天工(北京)科技有限责任公司 一种多工位旋转锯切设备

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB446767A (en) * 1934-11-26 1936-05-06 John Alfred Prestwich Improvements in or relating to cylinders for internal combustion engines and compressors
US2460024A (en) * 1945-05-19 1949-01-25 Superheater Co Ltd Method of making heat-exchange unit
US2792050A (en) * 1953-07-24 1957-05-14 Ray C Edwards Apparatus for manufacturing helically finned tubes
US2896426A (en) * 1957-03-01 1959-07-28 Carrier Corp Heat exchange construction
US3030292A (en) * 1956-08-03 1962-04-17 Parsons C A & Co Ltd Fuel elements for nuclear reactors
US3099071A (en) * 1963-01-14 1963-07-30 Moore Harrington Tool for cutting grooves in the flanks of screws
US3106958A (en) * 1961-06-06 1963-10-15 Modine Mfg Co Heat exchanger
US3134166A (en) * 1960-08-26 1964-05-26 Gen Electric Manufacture of heat exchange tubing
US3189087A (en) * 1958-03-06 1965-06-15 Green & Son Ltd Tubular heat exchangers

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB446767A (en) * 1934-11-26 1936-05-06 John Alfred Prestwich Improvements in or relating to cylinders for internal combustion engines and compressors
US2460024A (en) * 1945-05-19 1949-01-25 Superheater Co Ltd Method of making heat-exchange unit
US2792050A (en) * 1953-07-24 1957-05-14 Ray C Edwards Apparatus for manufacturing helically finned tubes
US3030292A (en) * 1956-08-03 1962-04-17 Parsons C A & Co Ltd Fuel elements for nuclear reactors
US2896426A (en) * 1957-03-01 1959-07-28 Carrier Corp Heat exchange construction
US3189087A (en) * 1958-03-06 1965-06-15 Green & Son Ltd Tubular heat exchangers
US3134166A (en) * 1960-08-26 1964-05-26 Gen Electric Manufacture of heat exchange tubing
US3106958A (en) * 1961-06-06 1963-10-15 Modine Mfg Co Heat exchanger
US3099071A (en) * 1963-01-14 1963-07-30 Moore Harrington Tool for cutting grooves in the flanks of screws

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3517576A (en) * 1965-03-24 1970-06-30 Gulf Research Development Co Cutting process
CN111215697A (zh) * 2020-03-02 2020-06-02 李远超 一种间距可调的分条设备
CN114769688A (zh) * 2022-04-29 2022-07-22 沈阳飞机工业（集团）有限公司 加工薄耳片深槽口的方法
CN114769688B (zh) * 2022-04-29 2024-03-08 沈阳飞机工业（集团）有限公司 加工薄耳片深槽口的方法
CN114769697A (zh) * 2022-06-15 2022-07-22 江苏辅星电子有限公司 一种铜散热片用的生产系统及制备方法

Also Published As

Publication number Publication date
GB1101811A (en) 1968-01-31
DE1776242A1 (de) 1974-02-28
NL6508074A (de) 1966-04-21
DE1452313A1 (de) 1969-01-23
GB1101812A (en) 1968-01-31
BE660122A (de) 1965-06-16
NL141411B (nl) 1974-03-15
DE1776242C3 (de) 1975-08-07
DE1776242B2 (de) 1975-01-02
FR1431159A (fr) 1966-03-11

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