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Publication numberUS2690782 A
Publication typeGrant
Publication date5 Oct 1954
Filing date3 Aug 1951
Priority date3 Aug 1951
Publication numberUS 2690782 A, US 2690782A, US-A-2690782, US2690782 A, US2690782A
InventorsTirone Stephen A
Original AssigneeFedders Quigan Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Machine for bending tubing
US 2690782 A
Abstract  available in
Images(4)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Oct. 5, 1954 5 TIRONE 2,690,782

MACHINE FOR BENDING TUBING Filed Aug. 3 1951 4 Sheets-Sheet l FjQl. I

Oct. 5, 1954 s. A. TIRONE 2,690,732

MACHINE FOR BENDING TUBING Filed Aug. 3, 1951 4 Sheets-Sheet 2 Fig); .2 5% 59 6 165 35 33 25 7 Imventor Sfepben A. 71m]? a,

1954 s. A. TIRONE 2,690,782

MACHINE FOR BEINDING TUBING Filed Aug 5, 1951 4 Sheets-Sheet 4 is? $2 106 v (2 72 -22 113114 5 13 9 Fig). 10. 71 108 I 11.?

U h- H 109 J 1; 4

, 3nventor 114 115 fle hanATjrone,

' Ct Qorneg Patented Get. 5, 1954 STTES OFFIE MACHINE FOR BENDING TUBING Appiication August 3, 1951, Serial No. 240,075

1 3 Claims.

This invention relates to a machine for bending tubing, and it has particular reference to a machine for bending long lengths of tubing back and forth to form a serpentine coil in which the successive runs are closely spaced, and are interconnected by return bends of relatively small radius.

Serpentine coils are extensively used in the refrigeration industry as condensers and evaporators, and it is common practice to form them by reversely bending a length of straight tubing a suificient number of times to provide the desired number of straight lengths or runs, which are successively connected to return bends of 180. commercially available for forming the coil by grasping it at an appropriate distance from one end and swinging the projecting portion around a die of circular cross section, thereafter advancing the tubing another increment, turning it over, repeating the operation. -A major' problem has been to form these bends on relatively sm ll radii without crushing, cracking, otherwise damaging the tubing at the bend, or without so disturbing the tubing that the flow and performance characteristics of the finished coil are seriously impaired.

When the bending radius is large compared to the tube diameter, existing equipment can form 180 bends without intolerable distortion. bending to a smaller radius, it has been proposed to insert a mandrel of some kind inside the tube, so that the metal wall could not collapse. 'il'iiis expedient, however, has not proved to be isfactory. A metal mandrel must be positioned with great accuracy, and liquid or sand mandrcls present subsequent cleaning problems. In any event, an internal mandrel alone is no guarantee against tube rupture, as the metal can crack from the inside out, as well as collapse when no mandrel is used. An additional disadvantage is, that in working relatively long lengths of tubing, say fifty to one hundred feet, the control. and manipulation of any type of beccines practical impossibility for scale production operations.

According to the present invention, a swing type tube bending machine is provided, organized for operation on tubing without the employment of any internal mandrel or support, and

by means of which tubing can be bent through arcs up to and over 180 on a small radius without serious distortion. As illustrative of the term small radius, machines made in accordance with this invention form serpentine coils from copper clad steel tubing having 0.375 inch out- Bending machines are well known and side diameter with a bend radius of 0.50 inch, thus spacing the runs on one inch centers. Such tubing is somewhat difficult to work at best, presenting many more problems than copper tubing, because of the greater hardness and toughness of the steel. For refrigeration service, many engineering specifications limit the permissible distortion of the bend to twenty per cent reduction in cross sectional area, irrespective of the tube diameter or bend radius. Reduction of in bends made on the present machine iy exceeds ten per cent, and the nature of the deformation from true circular cross section, or cut-of-roundness, is such that the hydraulic or flow characteristics, and therefore pressure drop through the coil, are not seriously impaired.

This improved bending machine, as will hereinafter be described in detail, includes a rotatable bending block or die having a semicylindrical and grooved end around which the bend is formed. Clamping means are provided to secure the tubing to the block in advance of the bend, and a grooved follower late is provided to engage the tubing, and force it into the end groove as the die is rotated. Mechanism is also provided to impose significant pressure on the follower plate during the movement of the die, and to release the pressure when the bend is completed, so that the tubing can be shifted for a subsequent operation.

The forming grooves in the die and follower plate, throughout the portions corresponding o the linear length of the bend, are not semicircular in cross section, but deviate therefrom into a somewhat semi-elliptical contour. Contrary to what might have been supposed, it has been found that if the tubing is gripped tightly around entire circumference, and is slightly deformed into oval shape with the major parallel to the plane of adjacent runs, it may be bent around the forming die to form a smooth return bend having a small radius of curvature compared to the tube diameter, and that no internal mandrel is required to accomplish this result.

These features and advantages, together with others, will be made more apparent from the following detailed description of a typical embodiment of the invention, illustrated in the accompanying drawings, wherein:

Fig. l is a plan of the machine, with a partially formed serpentine coil shown in full lines at the start of a bending operation, and in broken lines at the completion thereof;

Fig. 2 is a front elevation, with portions of the table broken away;

Fig. 3 is a fragmentary side elevation;

Fig. 4 is a section taken substantially on the line 44 of Fig. 3, showing particularly elements of the pressure applying mechanism;

Fig. 5 is an enlarged section on the line 5--5 of Fig. 1 or 4;

Fig. 6 is an additionally enlarged horizontal section through the die block and follower, taken at the completion of a bending operation;

Fig. 7 is a still further enlarged section on the line 1-1 of Fig. 6;

Fig. 8 is a section through a tube bend, along the line 8-3 of Fig. 6;

Fig. 9 is a perspective of a cam control memher for the pressure applying mechanism; and

Fig. 10 is an exploded perspective of two of the elements of the cam control member.

The mechanism is mounted on a table top or working surface 2| which may be conveniently positioned on a frame formed by welding or otherwise connecting upright legs 22 and horizontal stretchers 23 and 24. In the particular form shown in the drawings, the top 2| is supported above the main frame by spacer blocks 25 resting on corner plates 26, and it is retained by bolts 21. The top 2| is provided with a depressed portion 28 conveniently located adjacent one corner. As best shown in Fig. 5, a bearing housing boss 29 depends below an opening in the center of the portion 28, and in it are fitted spaced bearings 3| which rotatably support a ertical shaft 32, the upper end of which projects above the portion 28.

The upper end of the shaft 32 merges into and is integrated with a clamping block 33, which extends upwardl from the end of the shaft, and also outward from a shaft diameter. The end of the shaft, at a region just above the depression 28, is formed with a semicircular groove 34, which merges tangentially into horizontal grooves 35 and 36, formed on opposite faces of the block 33. The ends of the block 33 are provided with brackets 31 extending outwardly therefrom at right angles to the direction of the grooves 35 and 36, and these brackets are formed with aligned horizontal slots 38. The face of the block 33, above the groove 35, is formed with a hook 39, adapted to interengage with a similar hook 4| formed on a detachable clamping plate 42.

The plate 42 includes a vertical plane lower margin 43 formed with a longitudinal groove 44, with an angular portion 45 from which the hook 4! projects, and with a narrower vertical portion 43 adapted to enter between the brackets 31. When the hooks 39 and M are interengaged, the groove 44 is aligned with the groove 35 of the block 33, and these grooves can tightly encircle a section of tubing T, as is clearly shown in Fig. 6. A locking cam 41, provided with projecting trunnions 48 and an operating handle 49, is mounted between the brackets 31, the trunnions being loosely retained in the slots 38. When the handle 45 is swung counterclockwise, as viewed in Fig. 5, the arcuate ends of the cam 41 engage the inner faces of the block 33 and plate 42, thereby causing the plate 42 to pivot slightly about the fulcrum point between the hooks 39 and 4|, forcing the lower portion 43 of the plate 42 against the lower portion of the block 33, or against tubing positioned in the grooves 35 and 44.

It will be seen that the block 33 and plate 42 constitute relatively fixed and movable jaws of a pipe vise or clamp, wherein the tubing T may be securely retained against movement. The

exactly parallel.

grooves 35 and 44, in which the tubing is imprisoned, may be of semicircular contour, and have a radius substantially the same as that of the tubing to be worked upon, so that the tubing will be held against displacement, but at the same time will not be unduly crushed or deformed. When the handle 43 is swung in a clockwise direction, the cam 4'! is disengaged from the surfaces of the block and plate, and. the latter can then be detached. A lifting handle 5| is provided on the plate 42 to facilitate this operation. A relatively long operating handle 52 is secured to the outer face of the block 33 for rotating the shaft 32 about its own axis.

The recess 28 of the table top 2! is formed with a right angled depressed extension 54, in which are secured, by screws 55, a pair of tapered gibs 55, which provide a retaining bearing for a slide 5?. The inner end of the slide 57 terminates in transverse and upwardly extending flange 58, which is formed with a dovetail guide 59 to receive and retain a longitudinally slidable follower plate 5i. As shown in Fig. l, the plate 3! is normally retracted to the left by a spring 62, the ends of which are connected to a pin 33 on the table top, and a pin 54 (Fig. 6) on the end of the follower plate 8i. At the start of a bending operation, the left hand end of the follower 5! abuts the rim of the depression 28, which serves as a positioning stop.

The outer face of the follower 5| is formed with a longitudinal arcuate groove 55, the lead- .ing portion of which is disposed opposite the groove 34 of the shaft 32. The trailing portion of the groove 35 is adapted to face the groove 36 of the clamping block 33 at the completion of a bending operation, as illustrated in Fig. 6. It will be noted that the follower block 6| is longer than the block 33, so that, at the start of a bending operation, the extreme right end of the groove 65 slightly overlaps the groove 34. The slide 51 is herein shown as having been advanced or moved in its guides 56 toward the tubing T, to force the tubing tightly between the leading end of the groove and the shaft groove 34-. As the shaft 32 is rotated from the Fig. l to the Fig. 6 position, pressure applied to the slide 51, and therefore to the block 5!, progressively forces the tubing into the groove 34, while the trailing end of the tubing, and the follower block 6!, move to the right.

It will additionally be seen from Fig. 6 that, at the end of a full return bend formation, the groove 36 of the block 33 faces the trailing portion of the groove 65, and that it is slightly angularly disposed with respect thereto. The face of the block 33 containing the groove 36 is tapered with respect to the opposite face, so that the block 33 may be rotated slightly more than It has been found that the tubing tends to spring back at the bend, so that, if a bend of only 180 were made, the lengths would not be Accordingly, provision is made for some overtravel to compensate for this effect. As the block 33 is swung to its maximum extent, the trailing portion of the tubing T is clamped between the groove 36 and the trailing portion of the groove 55, to restrain the tubing from further forward movement. During the last few degrees of rotation, adjacent tube lengths are brought slightly out of parallelism, and the metal at the bend proper is slightly drawn further. Upon separation of the grooves 35 and 65, the spring back effect enables the tube lengths to return to true parallel relation.

assures Means are provided to apply substantial pressure to the tubing to force it between the grooves 3t and 35, and to maintain the pressure until the bend is formed. The details are best illustrated in Figs. 2, 3, 4, and 5. A pneumatic ram ii is bolted or otherwise secured to a bottom plate '32 of a frame including side rails 13 and a top rail it, which in turn is aflixed to the under side of the table top 2!. The piston rod '55 of the ram extends upwardly through the plate '12, and its exposed portion has connected thereto a cross bar 16, adapted to abut adjustable stop screws ll which are threaded into bracket arms F8, welded to the side rails '13.

.A pair of bearing plates 8!, welded to the top rail M, are provided with aligned bearing apertures in which is mounted a shaft 82, which carries a bell crank lever 33. One arm 84 of the lever is coupled to the end of the piston rod 75 by means of a bifurcated. yoke 85 threaded onto the end of the rod, and a pivot pin 85. lhe other arm Bl of the lever 83 is formed with a ball end positioned in a socket block 38, which is secured to the slide 5! by screws 89 (Fig. 1). An aperture 95 in the table top 2! permits the block as to slide back and forth with the slide 5?, as the piston rod '55 is reciprocated. It will be readily understood that, as the piston rod is elevated, the slide l is forced toward the shaft 32, and when the rod is withdrawn, the slide 51 is retracted to clear the tubing T. The adjusting screws ll limit the upward movement of the rod and therefore the maximum pressure which can be exerted on the work, which pressure can obviously be controlled within very narrow limits.

A platform 93 is suspended beneath the table top 2i by means of posts 93 and bolts 95 entering blind tapped holes in the top. An air control valve 36 is mounted on the platform 93, to receive air from a supply source through a line 91', and deliver it to the ram ll through a line 98. It may be pointed out here that the details of neither the valve 96 nor the ram H form any part of the present invention, as each device is a known article of commerce available in the United States. It will be sufficient to note that the valve 96 includes an actuating plunger 99, which may be depressed or released by movement of a lever llll pivoted to the valve casing. When the plunger as is depressed, air may flow through the valve to the cylinder of the ram ll, thus elevating its piston rod l5, and when the plunger is released, the air supply through the line 9? is cut oil, and the air in the ram ll bleeds back through the valve to atmosphere.

The admission of compressed air to the ram i! is controlled by the position of the shaft 32, through a cam its (Fig. 9), mounted on the lower end of the shaft. The cam comprises a concentric hub M23 formed with a segmental flange Hil having an upstanding peripheral rim 588 for the major portion of its length. The forward portion of the flange i9? is provided with depending boss 583, which is drilled to provide a bearing for a pin HE having an arcuate latch element or switch cam I I2 on its upper end. The lower end of the pin Ill projects beyond the boss N13, to receive a lever H3, to the outer end of which is connected a spring H4 extending to a stud i it on the hub N36. The spring 114 urges the latch H2 in a counterclockwise rotative direction, so that its tip normally abuts the hub Hi5 above the flange till, to provide a small exposed surface of the flange in front of the latch.

A cam lever H5 is pivotally mounted on the platform 93, and its free end is equipped with 9; depending roller i ll adapted to rest on the flange 40? in the notch formed between the end of the latch H2 and the hub I06. The lever H6 is normally urged to this position by a spring H8 extending from the midportion of the lever to a bracket H9 secured to the platform The edge of the lever engages the outer end of the valve lever WI, and, in this position, the plunger 83 is extended, corresponding to a condition of release of air from the ram H. A few degrees rotation of the shaft 32 causes the roller H! to ride outwardly on the convex surface of the latch H2, thereby depressing the valve plunger 99 through the conjoint displacements of the levers H6 and 131. As the shaft continues to rotate, the roller ill rides over the outer surface of the rim H33, retaining the valve open, until the trailing edge of the rim I08 passes the roller.

It will be seen from Figs. 4 and 9 that the arc swept out by the cam I I2 and rim I38 is less than and this diminution is determined by the diameter of the cam roller H1. The parts are so proportioned that, as the outer surface of the rim I08 completely clears the roller ill, the shaft 32 has rotated a full 180. At this instant, the spring H8 pulls the lever H6 against the hub I06, and inside the rim I08, thereby enabling the valve plunger 99 to move outwardly automatically and release the air pressure in the ram ll. When the shaft 32 is restored to the starting position, the roller abuts the inner surface of the latch H2 to swing it outwardly about its pivot Ill, thereby returning the lever H6 and latch M2 to their starting positions.

It has heretofore been noted that the pressure applied to the tubing between the shaft groove 34 and the leading portion of the follower groove 65 is substantial, and that these grooves are not truly semicircular in cross section. The grooves 35 and M, and the grooves 36 and trailing portion of the groove 65, may be semicircular, as they engage straight portions of tubing. As a practical matter, it does no harm to make the groove 65 of the same contour throughout, as the manual pressure applied in the overtravel of the block 33, to set the bend, will not cause any appreciable deformation. The nature of the grooves 34 and 65 is best shown in Figs. 6 and '7.

Assuming a machine proportioned to bend 0.375" outside diameter steel tubing, it will be seen from Fig. 7 that the grooves 3 and G5 are so contoured as to increase the overall dimension of the tubing, in a right section taken through the bend, and in the horizontal plane. Similarly, the overall dimension is decreased in the vertical plane, and therefore the tubing may be considered to be slightly flattened, or made outof-round, with the major axis in the plane of the coil. The dimensions given in Fig. 8, of D+0.0l.7" for the horizontal or major axis, and D0.040" for the vertical or minor axis, refer to tubing of the stated size and character, and these of course may be proportionately varied with nonferrous tubing, or tubing of other diameter. In practice, it is feasible to lay out the contours as three centered arches, which may be followed with sufficient accuracy with a grinding wheel, and to blend the several contours into each other, and into the adjacent semicircular contours, so that continuous smooth curves are obtained.

At the beginning of a coil forming operation, the shaft 32 and die block 33 are swung clockwise to the position shown in Fig. 1, with the slide 51 and follower 6! in retracted positions.

The leading end of a length of tubing T is then pushed over the table top 2| and into engagement with the groove 35, and the detachable clamping plate 42 is then looked to the block 33 to secure the tubing an appropriate distance from its leading end. The portion of tubing immediately in back of the clamped section is then located between the leading tip of the groove 65, and that portion of the shaft groove 34 which directly merges into the groove 35.

As the operating lever 52 is swung counterclockwise, the cam member I05 actuates the valve 96 to admit air to the ram 1 I, as heretofore described, thereby forcing the slide 57 and follower 61 against the tubing, and forcing the tubing between the grooves 34 and 65 to cause it to take substantially the cross sectional shape of the grooves 34 and 65. As the shaft 32 continues to rotate, the follower block 61 moves to the right, as shown in Fig. 6, and hence the successive increments of the grooves 34 and 65 act as mating portions of a forming die through which the tubing is drawn. That portion of the tubing which constitutes the return bend proper is therefore progressively formed and wrapped into the groove 34, and it will be seen that the increment of tubing undergoing working at any instant is tightly clamped about its entire circumference.

As heretofore noted, the cam I05 is of such arcuate length as to release the cam roller ll'l after 180 rotation, thus removing the pressure exerted on the tubing through the ram H. The slight additional rotation which may be effected by the taper of the leading face of the block 33 parent that, in its broader aspects, the invention is not limited to the precise details of the mechanisms specifically illustrated and described. It

is accordingly intended that the invention should be accorded a range of equivalents and scope commensurate with that expressed in the following claims.

I claim:

1. In a machine for bending tubing of circular cross section, a rotatable shaft formed with a circumferential groove, a clamping vise attached to the shaft and extending radially outward thereof, said vise being formed with mating arcuate grooves adapted to secure tubing tightly therebetween and tangentially to the shaft groove, 9. portion of said vise being in substantially radial alignment with said shaft the maximum thickness of said portion being substantially equal to the diameter of said shaft, a follower positioned adjacent the shaft and movable both radially and tangentially with respect thereto, said follower being formed with a groove disposed tangentially to the shaft groove, said follower and shaft grooves, in conjoint cross section, having an outof-round curvilinear periphery, the major axis of said conjoint follower and shaft grooves being normal to the shaft and the minor axis thereof being parallel to the shaft, the dimension of said grooves on said major axis being sufficiently greater than the normal outside diameter of said tubing and the dimension of said minor axis being sufficiently less than the normal outside diameter of said tubing to permanently flatten the bent portion of said tubing during the bending operation, and means for forcing the follower toward the shaft to clamp circular section tubing between the shaft and follower grooves and progressively bend and deform such tubing into said permanently flattened cross section as said shaft is rotated to bend the tubing.

2. In a bending machine, a working surface having a shaft rotatably mounted therein, said shaft extending above and below the surface, a circumferential groove formed in the shaft above the surface, a vise connected to the shaft to secure tubing therein and tangentially against the shaft groove, a slide and follower mounted on the surface for movement toward the shaft in a radial direction, said follower being slidably mounted on the slide for movement tangentially of the shaft, said follower being formed with a longitudinal groove adapted to cooperate with the shaft groove to grip tubing when the slide is moved toward the shaft, power means for moving the slide and follower toward the shaft, a cam control member mounted on the shaft below the surface, said member having a hub, a pivoted latch extending outwardly from the hub, and a dwell portion of limited arcuate length contiguous with the pivoted end of the latch, and a cam lever pivotally mounted below the surface for displacement by the latch and dwell portion of the cam, means governed by the cam lever for energizing the power means, the lever and cam being so related that the lever is positioned against the hub adjacent the latch to deenergize the power means at the initial starting position of a bending operation, the lever is displaced as the shaft is rotated to energize the power means, is released for return to demergized position as the dwell portion clears the lever, and is restored to initial position when the shaft is rotated in a reverse direction to the starting position.

3. A machine as defined in claim 1 in which the portion of said vise in substantially radial alignment with said shaft is provided with grooves in the opposite faces thereof such grooves being at a slight angle to each other and in which the opposite faces of said portion are at a slight angle to each other whereby the shaft may be rotated more than one hundred eighty degrees during the bending operation to set the bend at a radius substantially equal to the radius of the groove in the shaft.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 56,519 Briggs July 24, 1866 361,398 Daniels Apr. 19, 1887 369,166 Daniels Aug. 30, 1887 1,013,839 Cox Jan. 2, 1912 1,155,042 Coron Sept. 28, 1915 1,262,882 Warner Apr. 16, 1918 1,410,294 Halliwell Mar. 21, 1922 1,450,317 Beers Apr. 3, 1923 1,485,731 Stangbye Mar. 4, 1924 1,714,083 Frank May 21, 1929 (Other references on following page) Number 9 Name Date Rode Feb. 25, 1930 Murray Mar. 11, 1930 Harvey Sept. 16, 1930 Olin Dec. 8, 1931 Meyer Mar. 14, 1933 Sachleben May 11, 1937 Segre Mar. 4, 1941 Parker Dec. 22, 1942 Parker Dec. 22, 1942 Bower Sept. 12, 1944 Lancaster Mar. 20, 1945 Number Name Date Shaw Nov. 16, 1948 Littell Jan. 10, 1950 Wildman Sept. 18, 1951 FOREIGN PATENTS Country Date Great Britain May 8, 1930 France May 3, 1932 Great Britain Oct. 3, 1934 Great Britain May 31, 1949

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US56519 *24 Jul 1866 Improvement in clamps for holding saws
US361398 *19 Apr 1887 Device for bending pipe
US369166 *30 Aug 1887 Device for bending pipe
US1013839 *3 Jun 19092 Jan 1912Matthew T CroninPipe-bending machine.
US1155042 *23 Feb 191528 Sep 1915Omer CaronPipe-bender.
US1262882 *19 Dec 191616 Apr 1918Williams White & CompanyForming and rolling machine.
US1410294 *17 May 191921 Mar 1922Gen ElectricValve-operating mechanism
US1450317 *1 Oct 19193 Apr 1923Beers William HPipe-bending machine
US1485731 *4 Aug 19224 Mar 1924Oliver Stangbye IdarCable-splicing device
US1714083 *3 Jun 192621 May 1929Greenpoint Metallic Bed Co IncTube-bending machine
US1748732 *25 Jul 192725 Feb 1930Marquette Tool & Mfg CoValve-operating mechanism
US1750537 *12 Jan 192811 Mar 1930Thomas GasparicValve-operating mechanism
US1775761 *23 Feb 192616 Sep 1930Steel And Tubes IncAutomatic air clamp and release for tubular benders
US1835322 *23 Oct 19298 Dec 1931Atlas Imp Diesel Engine CompanSpray valve control mechanism for internal combustion engines
US1901762 *6 Feb 193114 Mar 1933American Welding Mfg CoBending apparatus
US2080095 *3 Sep 193511 May 1937Sachleben Edward HTube shaping tool
US2233458 *17 Apr 19404 Mar 1941Massimo SegreClamping device
US2306223 *31 Mar 194122 Dec 1942ParkerAutomatic tube bending machine
US2306224 *31 Mar 194122 Dec 1942ParkerAutomatic tube bending machine
US2357873 *19 Oct 194212 Sep 1944Pines Engineering CompanyTube-bending machine
US2371695 *14 Sep 194220 Mar 1945Boeing Aircraft CoTube bender
US2453868 *20 Feb 194716 Nov 1948Pedrick Tool & Machine CompanyApparatus for automatically bending work such as tubing into serpentine coils
US2494396 *31 May 194610 Jan 1950Littell Machine Co F JAir valve with adjustable shutoff control
US2568691 *11 Mar 194818 Sep 1951American Welding & Mfg CompanyAdjustable and yieldable male bending die
FR729876A * Title not available
GB328868A * Title not available
GB417656A * Title not available
GB624227A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2986195 *9 Jul 195630 May 1961Imp Eastman CorpTube bending machines
US3279236 *12 Mar 196518 Oct 1966Lance Bruce JTube bending device
US4112728 *26 Jan 197812 Sep 1978Deutsche Babcock AktiengesellschaftDevice for bending pipes
US9669499 *30 Nov 20106 Jun 2017Denso CorporationDouble-wall pipe, method of manufacturing the same and refrigerant cycle device provided with the same
US20110073208 *30 Nov 201031 Mar 2011Denso CorporationDouble-wall pipe, method of manufacturing the same and refrigerant cycle device provided with the same
Classifications
U.S. Classification72/168, 269/239, 251/251, 137/560, 72/154, 72/169
International ClassificationB21D11/07, B21D11/00
Cooperative ClassificationB21D11/07
European ClassificationB21D11/07