US3688550A

US3688550A - Crushing and bending of sections of members

Info

Publication number: US3688550A
Application number: US935A
Authority: US
Inventors: Kenneth Ernest Stanley
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-01-07
Filing date: 1970-01-06
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: FR2027884A1; DE2000354A1; NL7000148A; FR2027884B1; CH524410A; BE744128A; AU1010070A; ES375212A1; GB1292604A

Abstract

A method of crushing and bending an end section or an intermediate section of a tube comprises placing in a cradle of a die of a press a part of the tube including the section, and moving a punch of the press towards the die such that the section and the remainder of the tube part are bent one relatively to the other and one wall portion of the section is crushed inwardly towards a diametrically opposite wall portion of the section. The tube having a section so crushed and bent can be connected to another tube, for example, by disposing the section face-to-face with a complementarily shaped portion of the other tube such that the remainder of the part extends away from the latter portion, and then, for example, welding or bolting the section to the other tube.

Description

Elite States atet Stanley Sept. 5, 1972 [54] CRUSHING AND BENDING OF 1,823,028 9/1931 Caldwell ..113/1 16 SECTIONS OF MEMBERS Primary Examiner-Lowell A. Larson [72] Inventor. Kenneth Ernest Stanley 1, Green Acre, Aylesbury Englami Attorney-Waters, Roditi, Schwartz & Nissen [22] Filed: Jan. 6, 1970 [57] ABSTRACT PP N03 935 A method of crushing and bending an end section or an intermediate section of a'tube comprises placing in [30] Foreign Application Priority Data a cradle of a die of a press a part of the tube including the section, and moving a punch of the press towards 1969 Great Bmam "998/69 the die such that the section and the remainder of the tube part are bent one relatively to the other and one "72/369, 29/ wall portion of the section is crushed inwardly towards n a diametrically opposite wall portion of the section. Field Of 'r tube having a Section so crushed and bent can be 72/380 29/150 113/116 116 UT connected to another tube, for example, by disposing the section face-to-face with a complementarily [56] References and shaped portion of the other tube such that the UNITED STATES PATENTS remainder of the part extends away from the latter portion, and then, for example, welding or bolting the 2,285,275 6/ 1942 Harder ..72/369 Section to the other tube 774,159 11/1904 Cook ..29/150 3,374,532 3/1968 Zenhausern ..72/369 17 Claims, 37 Drawing Figures 5A 5 2 5.1 "i," v

6 5C -SC l i 1 3A 2 mimosa? s we SHEET 030F 13 P'A'TE'NTEDSEP 5 I972 SHEET DQUF 13 FIG. H

PATENTEDSEP smz 3.688550 SHEET 080F 13 P'A'TENTEDsEP 51912 3.688.550 sum near 13 PATENTEDSEP 5 I972 SHEET 100! 13 PA'TENTEDsEP 5:912 3.688.550 sum nor 13 PATENTEDsEP 5:912 3.688.550

sum IBM 13 PATENTEDSEP 5 m2 SHEET 13UF 13 CRUSHING AND BENDING OF SECTIONS OF MEMBERS According to one aspect of the present invention, there is provided a method of crushing and bending a section of an elongate member, comprising placing in a die of a press a part of said member including said section, and moving one of said die and a punch of said press towards the other, such that said section and the remainder of said part are bent one relatively to the other and one wall portion of said section is crushed inwardly towards a diametrically opposite wall portion of said section.

According to another aspect of the present invention, there is provided a method of connecting together an element and a member having a crushed and bent section and produced by the method set out above, wherein said crushed and bent section is disposed faceto-face with a complementarily shaped portion of said element such that said remainder extends away from the latter portion, and then said member is connected to said element by connecting means.

Although the elongate member to which the present crushing and bending method is applied is preferably a metal tube, nevertheless it could be a solid rod of suitable material, or it could be a member of plastics material deformable by impact.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIG. 1 shows a side elevation of a punch and a die of a press in use in a method of crushing and bending an end section of an elongate member, in this case a metal tube, but before crushing and bending of the end section,

FIG. 2 shows a sectional view taken on the line II--II of FIG. 1, but with the end section crushed and bent,

FIG. 3 shows a side elevation of a joint between the tube and an element, in this case another tube, and incorporating the crushed and bent end section,

FIG. 4 shows a sectional underneath plan view of the oint,

FIG. 5 shows a diagrammatic perspective view of a modified tube usable in thejoint,

FIG. 6 shows a view similar to FIG. 5 of another modified tube usable in the joint,

FIG. 7 shows a perspective view of a tube according to FIG. 5 having punched holes,

FIG. 8 is a diagrammatic perspective view of two elements, in this case rods, interconnected by a tube to each end of which has been applied the crushing and bending method,

FIG. 9 is plan view of a part of a geodetic structure formed of a network of identical tubes to each end of each of which the crushing and bending method has been applied,

FIG. 10 is a plan view of one of the tubes of this.

structure,

FIG. 1 l is a side elevation ofthe tube of FIG. 10,

FIG. 12 is a perspective view of a modified version of the joint of FIG. 3, but with the two tubes shown disconnected,

FIG. 13 is a side elevation of another modified version of thejoint of FIG. 3,

FIG. 14 is a plan view of a strap of the version of FIG. 13,

FIG. 15 is a section on the line XV-XV of FIG. 14,

FIG. 16 is a perspective view from above of a further modified version of the joint of FIG. 3,

FIG. 17 is a sectional underneath plan view of the version of FIG. 16,

FIG. 18 is a perspective view of a joint incorporating a short tube to which has been applied the crushing and bending method with crushing of the tube along its whole length,

FIGS. 19 to 23 are side elevations of respective different manners of improving the rigidity of joints including the crushed and bent end section,

FIG. 24 is a side elevation of a modified version of the punch and die of FIG. 1 in use in a modified version of the method of FIG. 1,

FIG. 25 is a sectional end view of the punch and die of FIG. 24,

FIG. 26 is a section on the line XXVI-XXVI of FIG. 24, but omitting a tubeto which the method is being applied,

FIG. 27 is a fragmentary plan view of a tube to which the method of FIG. 24 has been applied,

FIG. 28 is a side elevation of another modified version of the punch and die of FIG. 1 in use in a modified version of the method of FIG. 1,

FIG. 29 is a section on the line XXIX-XXIX of FIG. 28,

FIG. 30 is a perspective view of one end of a metal tube to which end has been applied the crushing and bending method of FIG. 28,

FIG. 31 is a side elevation of a joint between that tube and another tube,

FIG. 32 is a perspective view of a further modified version of the punch and die of FIG. 1 for use in a modified version of the method of FIG. 1,

FIG. 33 is a side elevation of a joint incorporating a tube to which has been applied the crushing and bending method ofFIG. 32,

FIG. 34 is a section on the line XXXIVXXXIV of FIG. 33,

FIG. 35 is a framework incorporating tubes to which have been applied the methods of FIGS. 1 and 32,

FIG. 36 is a perspective view of a joint between the tube of FIG. 33 and an element, in this case a plate, and

FIG. 37 is a section on the line XXXVII-XXXVII of FIG. 36.

Referring to FIGS. '1 and 2, the punch I has a horizontal cross-section as shown in FIG. 2, namely that of a rectangle 1A with a segment 18 of a circle added at one of its shorter sides. Its vertical section in a plane perpendicular to the plane of FIG. 1 is basically of the same shape as its horizontal section. The die 2 is formed with a cavity 3 and has fixed thereto an upright block 4 serving both as a guide for the punch 1 and as an end stop for the tube 5. The cavity 3 is of a horizontal section similar in size and shape to that of the punch 1, except that its horizontal section is lengthened at 3A to take a double thickness of the tube wall of the tube 5 and is widened slightly at 3B to provide clearances for taking account of the spread of the metal of the tube. That wall 3C of the cavity furthest from the block 4 is concave and part-cylindrical. The uppermost surface of the die 2 is formed with a semi-cylindrical recess 6 forming a cradle for receiving the end part 5A of the tube 5. The tube 5 is clamped in the recess 6 by some clamp means (not shown) which can consist either of a clamp secured to the die 2, or of a spring-loaded pin mounted on the punch block and clamping the tube during the descent of the punch l. The recess 6 merges smoothly into the cavity 3 at a surface of minimum radius y shown in FIG. 1. At its side furthest from the block 4, the leading end of the punch l is formed with a rounded corner 1C at which the convex part-cylindrical face ID of the circular segment 13 merges with the convex part-cylindrical underneath face 1E of the punch.

In the crushing and bending method, the end part A of the tube 5 is placed in the die 2 such that the end part 5A overlaps the cavity 3 and the end section SE to be crushed and bent lies substantially directly between the cavity 3 and the punch 1. After clamping of the tube 5 in the recess 6, the punch l is lowered vertically into the cavity 3 and in so doing bends downwardly the end section 5B, relatively to the remainder of the tube, into a position against the part-cylindrical wall 3C of the cavity 3 and simultaneously crushes the end section SB radially of itself against the wall 3C. The section 5C of the tube 5 adjacent to the section 5B remains unbent and uncrushed, although there is of course a short transitional section between the

sections

5B and 5C.

FIGS. 3 and 4 show the crushed and bent end section 58 fitted tightly against a vertical tube 7 of the same external diameter as the tube 5. The end section 58 is drilled or pierced, and the tube 7 is drilled or pierced diametrically, to receive a bolt 8 having a radiussed head. Co-operating with the bolt 8 to fix the

tubes

5 and 7 together is a radiussed washer 9 and a nut 10. Radiussing of the head of the bolt 8 and of the washer 9 increases the stability of the joint. Alternatively, the end section 5B is pierced with a shouldered punch so as to provide a flat on which the nut can sit. Because of the dome so formed, the strength of the end section 58 is thereby considerably increased.

By using the described method to crush and bend an end section of a three-fourths inch outside diameter x.040 inch electrically resistance welded steel tube, a radius y of five-sixteenths inch has been obtained without rupturing of the tube.

The crushing and bending method described is a cheap and simple way of pressing the end section of the tube to form a U-channel so that another tube can be mated and secured to it at an angle by bolting, rivetting, welding, or brazing, for example. Because of the stresses set up in the manufacture of welded steel tubes, it is desirable to place such a tube in the die of the press tool such that the seam weld lies on a neutral axis with .:gard to the forming forces applied to it by the punch and die, otherwise the tube may split along the weld. When the press is operated, the punch descends and collapses the upper portion of the wall of the end section of the tube and swages it into the U-channel form required. For releasing the finished component, a conventional press tool technique, such as ejector pins, is used. Only one cycle of the press is required to produce the finished component.

The example described with reference to FIGS. 1 to 4 has the following advantages:

1. Products made of T-jointed tubing are cheaper to produce with this method than when their T-joints are formed by known methods.

2. A press with simple press tools and commonly available in industry is used to crush and bend the ends of tubes, instead of expensive bending machines being required to be used.

. Because the bend in the tube can be of relatively small radius, the axis of the main section of the tube can be relatively near to the axis of a bolt used for securing it to another tube. This gives increased rigidity of the joint produced.

. By using the described T-joint in tubular products substantial savings on packaging and freight costs can beobtained because the products can be designed as knock-down products for assembly by the customer.

5. The T-joint described is sufficiently rigid to replace welded T-joints in many products such as tubular furniture, car seats, roof racks, toys and benches. Moreover, the products can be made more quickly and by unskilled labor.

If desired, opposite end sections of the tube 5 can be simultaneously formed as shown in one cycle of the press merely by incorporating two identical punches and two identical dies in one tool set. Similarly, a number of tubes can be correspondingly formed at one or both ends by having single or double sets of press tools placed side-by-side. It will be appreciated that the number of tubes which can be so formed in one cycle will depend mainly on the ease with which the tubes can be loaded into and removed from the die set, the tonnage of the press concerned, and the diameter, wall thickness and material of the tubing.

To allow considerable variation in the position of the end section 58 relatively to the tube '7, the latter can be of the form shown in FIG. 5 or 6, in which the tube is drilled or pierced with a plurality of pairs of diametrically opposite through holes 30. The pairs of holes are spaced apart along the tube by the axial distance a which is, for example, three-fourths inch in FIG. 5, and one-half inch in FIG. 6; and are regularly staggered through a constant angle a which is for example, in FIG. 5, and 60 in FIG. 6. The holes 30 are preferably made by punching using two diametrically opposite punches to make each pair of holes, the two punches being moved towards each other from outside the tube, but being stopped before they reach the tube axis. FIG. 7 shows a tube having its holes 30 arranged according to FIG. 5 and formed by such punching, the resulting burrs 31 being produced on the inside of the dimpled holes 30.

Tubes as shown in FIG. 5, 6 or 7, are very suitable for use as the tubes of a system of interconnected tubes, and whereas the joints between the tubes are advantageously of the form shown in FIGS. 3 and 4, other forms of joints can be used as well.

It will be appreciated that the crushed and bent end section 58 can be of many different shapes and be made at many different angles to the remainder of the tube 5 merely by changing the shapes and orientations of the forming faces of the punch and the die.

FIG. 8 shows the tube 5 connected between two rods 32 which are perpendicular to each other. It will be un derstood that in this case the two crushed and bent end sections 58 of the tube 5 also extend perpendicularly to each other.

Tubes each having its opposite end sections crushed and bent and extending in respective opposite directions are particularly suitable for use in a geodetic structure, for example a dome framework as shown in FIG. 9. In this structure the tubes are distributed in groups, the tubes of each group being equi-angularly spaced through an angle x in a star formation. Each tube extends from the center of one star formation to the center of another and has each section 58 thereof fastened, for example bolted or welded, to the uncrushed, unbent section 5C of an adjacent tube 5. An individual tube 5 of the structure of FIG. 9 is shown in FIGS. 10 and 11. The angle x between the end section 513 and the adjacent section 5C of the tube 5 is equal to the angle between each two adjacent tubes of the structure in FIG. 9, the angle x in the case shown being 60. FIG. 11 illustrates that the tube 5 is bent to the form of a circular arc of a radius equal to the radius of the dome. The bending of the whole tube 5 for this purpose can be performed either before or after crushing and bending of the end sections 58. A preferred method of. forming a section 58 at 60 to the section 5C is firstly to apply the method of FIGS. 1 and 2 to form the crushed and bent section 5B at an angle of 90 to the section 5C, and then to bend the section 5B through the additional 30 in a press, for example at the same time as a hole for the bolt 8 is formed.

Referring to FIG. 12, the section 5B, after crushing and bending, has had half-pierced therefrom four vertical lugs 40, the holes 41 being left by the half-piercing. Each lug 40 consists of a portion 40A of a height equal to the height of vertical rectangular slots 42 through the wall of the tube 7, and a portion 40B of less height than the slots 42 and disposed between two notches 40C formed in the top and bottom edges of each lug 40. Each portion 40A is attached to the section 58 by way of the adjacent portion 408. Each hole 41 has a pair of lugs 40 half-pierced therefrom, and the lugs of each pair extend parallel to each other, the spacing between their outside faces being virtually the same as the horizontal width of each slot 42. The slots 42 are regularly staggered through a constant angle about the axis of the tube 7 and are spaced a constant distance apart along the tube. The spacing between any two slots 42 disposed one vertically above the other is equal to the spacing between the pairs of lugs 40. Thus, the pairs of lugs 40 can have their portions 40A inserted through two slots 42 of which one is disposed vertically above the other, and then the tube 5 is lowered such that the bottom edges of the two slots 42 in question engage with the notches 40C in the bottom edges of the lugs 40. The tube 5 is now prevented by the lugs 40 from moving relatively to the tube 7 in any manner except upwardly.

In FIGS. 13 to 15, the connection between the tube 5 and the tube 7 is infinitely adjustable along the tube 7. For this purpose, the tube 5 is connected to the tube 7 by solely an endless steel strap 43 embracing the

tubes

5 and 7. A portion 43A of the strap 43 bears against the inside of the bend at the adjacent end of the tube 5, while the opposite portion 433 of the strap 43 engages the tube 7. The portion 43B is of elongate cross-section with a sharp inside edge 43C engaging the tube 7, and the portion 43A may be of identical cross-section if so desired, but those portions of the strap 43 joining the

portions

43A and 43B are of circular cross-section. It will be understood that application to the tube 5 of a downward load as indicated by the arrow L in FIG. 13 will cause the edge 43C to bite into the outside surface of the tube 7 and thus prevent the tube 5 from sliding down the tube 7 under the load, but, nevertheless, on removal of the load, the tube 5 and the strap 43 can be readily adjusted to any desired position along the tube 7 Referring to FIGS. 16 and 17, the section 58 is modified in having its longitudinal edges 44 turnedback. This is achieved by suitable shaping of the forming faces of the punch I and the die 2, the turned-back longitudinal edges being formedsimultaneously with the crushing and bending of the section 5B. The edges 44 are substantially parallel to each other and to a plane containing the axes of the

tubes

5 and 7, which are perpendicular to each other. However, the edges 44 are oblique to the axis of the tube 7, which axis of course extends in the direction of movement of the punch l relatively to the die 2. The tube 7 is embraced by a short channel-form piece 45 which has its free longitudinal edges 46 parallel to each other and to the edges 44 and turned inwardly. The

edges

44 and 46 extend downwardly and outwardly away from the base of the piece 45. An internally threaded nipple 47 in the base of the piece 45 receives a grub screw 48 for tightening against the outside surface of the tube 7. The upper rim 49 of the piece 45 is thickened to be capable of receiving hammer blows without deformation. To secure the tube 5 to the tube 7, the section 58 is placed face-to-face against the tube 7 as shown, and then the piece 45 is lowered to engage its edges 46 behind the edges 44. Thereupon, the piece 45 is driven downwardly by hammer blows to press the section 58 firmly against the tube 7 by the wedging action of the

edges

44 and 46. Finally, the grub screw 48 is tightened to prevent the piece 45 from being accidentally knocked upwardly. It will be appreciated that the tube 5 can be adjusted to any desired position along the tube 7 after release of the screw 48 and the wedging action.

The joint shown in FIG. 18 consists of two metal rods 50 and 51 which are of circular cross-section and are disposed perpendicularly to each other. These are connected together by a crushed and bent short metal tube 52 welded to the rods 50 and 51. The member 52 has been formed in a punch-and-die arrangement such as is shown in FIGS. 1 and 2, except that the punch I has an extension of which the lowermost face is semi-cylindrical and enters the recess 6 to crush the remainder of the short tube at the same time as the end section of the short tube corresponding to the end section 58 is crushed and bent. The forming faces of the punch are of a radius identical to the radius of the rods 50 and 51, whereby the member 52 fits snugly on the rods 50 and 51.

It may be that in certain circumstances a joint such as shown in FIGS. 3 and 4 is not sufficiently rigid. In that case, as shown in FIG. 19, the joint can be strengthened by providing through the tube 7 a self-tapping screw 53 screwed into metal of the outside of the bend in the tube 5. A spacer 54 limits pulling of the tube 5 towards the tube 7 by the screw 53. The screw 53 is of course disposed as far as practicable from the axis 8' of the bolt 8.

In FIG. 20, the section 58 is shown projectionwelded at 55 to the tube 7. To strengthen the joint, a member 52 as shown in FIG. 18 is illustrated projection-welded to the tube 7 and to the uncrushed, unbent section C of the tube 5.

Another manner of strengthening the joint of FIGS. 3 and 4 is shown in FIG. 21, in which a gaiter S6 encircles the section 5C of the tube 5 and is fixed thereto in some manner, for example shrink-fitted thereto. The gaiter 56 has an extension 56A which fits snugly against the outside surface of the tube 7 and tends to prevent turning of the tube 5 about the axis 8' in both senses.

FIG. 22 shows a version in which a short length of tube 57 has been inserted in the end of the tube 5 before crushing and bending of the section 58 and has thus been crushed and bent simultaneously with that section.

With regard to FIG. 23, the joint between the

tubes

5 and 7 is again strengthened using the member 52, but this time the

parts

5, 7 and 52 are fixed to one another solely through rings 58 crimped or otherwise secured thereto.

Under certain conditions, it may be required that one of the longitudinal edges of the section 58 should project further than the other from the uncrushed, unbent section SC in an axial direction of the section 5C, while, nevertheless, these longitudinal edges remain parallel to each other and the section 58 remains of circular arc shape in cross-section. Such a version is shown in FIG. 27 and is produced using the punch 1 and the die 2 of FIGS. 24 to 26. In this, the vertical part-cylindrical forming face ID of the punch, and the corresponding vertical part-cylindrical forming wall 3C of the recess 3 are offset relatively to the vertical plane containing the axis of the recess 6. The lowermost face 15 of the punch l is again radiussed to promote the progressive collapse of the section SB of the tube 5 during crushing and bending. There is of course provided between the face 1D and the wall 3C as seen in plan a gap 59 to receive two thicknesses of the wall of the tube 5.

With the tube 5 already described, the tube 7 is received at the outside of the bend in the tube 5. It may be desired instead to have the tube 7 received at the inside of the bend in the tube 5, as shown in FIG. 31, in which the crushed and bent end section SF of the tube 5, while still of U-channel shape and fitting snugly against the outside surface of the tube 7, has its concave external surface facing towards the tube 5. This formation at the end of the tube 5 can be obtained by means of the punch l and the die 2 shown in FIGS. 28 and 29. The punch 1 has a vertical part-cylindrical concave face 1F merging at its lower end with a horizontal part-cylindrical concave face 10. The forming vertical wall 3D of the recess 3 is of part-cylindrical convex shape and is thus complementary to the face 1F The wall 3D merges into the wall of the part-cylindrical recess 6 of the die 2. When the punch 1 is lowered into the recess 3, the face promotes the downward bending of the end section 5F relatively to the remainder of the tube 5, and later the face 1F continues the downward bending of the end section 5F and. crushes it against the wall 3D, so that the end of the tube to which this method has been applied takes on the appearance shown in FIGS. 28 to 30. There is of course provided between the face IF and the wall 3D as viewed in plan a gap 60 dimensioned to receive two thicknesses of the wall of the tube 5.

It will be understood that the end section 5F may be fixed to the tube 7 by bolting as indicated at 8' in FIG. 31, rivetting, welding, or brazing, for example.

It may be desired to provide a joint in which, instead of an end section of a tube being mated to a complementarily shaped portion of an element as already described, an intermediate section of the tube is mated to this complementarily shaped portion. This can be achieved using the punch and die which are shown in FIG. 32 and which produce, on a tube 5 as shown in FIGS. 33 and 34, a crushed intermediate section 61 which is bent relatively to the remainder of the tube 5. This section 61 has its cross-section of the shape of a circular arc and has its concave external surface at the outside of the bend in the tube 5, whereby the tube 7 is received at the outside of this bend. FIG. 32 shows the punch and die for use in producing the crushed section 61 of the tube 5. Formed in the top surface of the die are two co-axial part-cylindrical recesses 71 having their axis horizontal and forming respective cradles for receiving the tube 5. Also formed in the die 70 is a recess 72 which is much deeper than the recesses 71 and which has at its bottom a forming wall 73 of convex part-cylindrical shape, the axis of the wall 73 being horizontal and lying in the same vertical plane as that containing the axis of the recesses 71. Joining the ends of the wall 73 to the inner ends of the walls of -the recesses 71 and merging smoothly therewith are two semi-cylindrical concave walls 74, the axes of which converge downwardly. The punch 75 is guided so as to be vertically displaceable and is formed at its underneath with a concave, part-cylindrical forming face 76 which, in the fully lowered position of the punch 75, covers the forming wall 73 at a spacing therefrom equal to two thicknesses of the wall of the tube 5. Merging at their lower ends with the face 76 are two semi-cylindrical faces 77 which are provided at respective opposite sides of the punch 75 and which have their axes parallel to the axes of the walls 74. When the punch 75 is in its fully lowered position, the axes of the faces 77 in fact coincide with the respective axes of the walls 74. In use of the punch and die of FIG. 32, a straight part of the tube 5 is laid in the recesses 71 with an intermediate section of this straight part extending over the recess 72. The punch is now lowered so that the face 76 contacts the intermediate section and displaces it downwardly. This causes the two sections of the tube 5 disposed axially outwardly of the face 76 to bend in a vertical plane upwardly towards the faces 77 until they are encircled by the walls 74 and the faces 77 in the lowermost position of the punch 75. Simultaneously, the intermediate section is crushed between the wall 73 and the face 76 to assume the shape shown in FIGS. 33 and 34.

By simply altering the radius of the wall 73, the radius of the concave external surface of the crushed section 61 can be adapted to the radius of the tube 7 on which it is to be seated.

A tube 5 formed with a crushed intermediate section 61 and two crushed end sections 58 is particularly useful in the construction oflattices, such as shown in FIG. 35, in which two tubes 5 are fixed by way of the scctions 58 and 61 between two parallel supporting tubes 7.

Both the end section 58 and the intermediate section 61 may mate with a complementarily shaped portion which has been displaced out of the plane of a plate. FIGS. 36 and 37 shows such an arrangement in respect of the intermediate section 61. Here, a so-called hogback 84) has been pressed out of a plate 81, and holes have been punched out of the hogback 80 and the section 61 and have been aligned to receive the bolt 82 of a nut-and-

bolt connection

82, 83. The hole in the section 61 for receiving the bolt 82 may be formed either after the crushing of the section 61, or be formed simultaneously with that crushing.

The joints described with reference to the drawings have the advantage that their shapes facilitate brazing and soldering because of the capillary attraction set up between the tubes and 7 to be joined. Another advantage is that, simultaneously with crushing of the

section

5B or 61, projections can be readily formed on the section to enable it to be speedily resistance welded to the tube 7. The major advantage of the examples described with reference to the drawings is that it is possible to mass produce crushed and bent tubes and rods with their cost of production and the radii of curvature of their bends being much less than with known methods.

In order to reduce the friction between the corner 1C and the tube 5 during crushing and bending in the version of FIGS. 1 and 2, and thus to reduce roughening of the surface of the tube 5, it is possible to mount in the corner 1C a wheel or ball which corresponds in radial section to the corner 1C and rolls on the tube 5 during crushing and bending. A similar modification may of course be made in the versions of FIGS. 24 to 26, FIGS. 28 and 29, and FIG. 32.

It may in certain circumstances be desired to have a fluid flow through the joint shown in FIG. 10, for example. In practice, it has been found that the free end of the section 5B can be made fluid-tight by the crushing described, while the opposite end of the section 58 remains not fluid-tight. Thus, by forming two holes, one in the inner wall of the section 58 at this opposite end, and the other in the wall of the tube 7, the interior of the section 5C has been communicated with the interior of the tube 7. The holes were formed prior to assembly and welding of the joint, during which a compressible sealing ring encircling the two holes was inserted and compressed between the inner wall of the section 58 and the wall of the tube 7. Fluid was then able to flow through the

tubes

5 and 7, the sealing ring preventing leakage of the fluid from the gap between the two walls.

WHAT I CLAIM IS:

I. A method of crushing and bending a section of a tube comprising placing in a die of a press a part of said tube including said section, and moving one of said die and a punch of said press towards the other to crush one wall portion of said section inwardly towards a diametrically opposite wall portion of said section so that said section acquires a double-walled channel form extending along said section and to bend said section and the remainder of said part one relative to the other so that said remainder extends from the base of said channel in a direction away from the mouth of said channel.

Ill)

2. A method according to claim 1, wherein after the crushing, each of said one wall portion and said opposite wall portion is of a cross-sectional shape of substantially the form of a circular arc.

3. A method according to claim ll, wherein after the crushing, each of said one wall portion and said opposite wall portion is of substantially constant crosssection throughout its length.

4. A method according to claim 1, wherein said part and said section are an end part and an end section, respectively, and said end part is placed in said die such that said end part overlaps a recess in said die and that said end section lies substantially directly between said recess and said punch, and one of said die and said punch is moved towards the other such that said punch penetrates said recess and in so doing bends said end section, relatively to said remainder, into a position against a suitably shaped wall of said recess and simultaneously crushes said end section radially against said wall.

5. A method according to claim 4, wherein said wall of said recess is concave, and said punch has a convex face which crushes said section against said wall.

6. A method according to claim 5, wherein said face and said wall are each asymmetrical throughout their lengths with respect to a plane extending in said direction and containing the longitudinal axis of said part when placed in said die, whereby said section after drushing and bending has its longitudinal central plane oblique to that of said remainder.

? 7. A method according to claim 4, wherein said part is placed in said die such that it is supported by a cradle df said die, said cradle extending transverse to the direction of movement of said one of said punch and said die towards the other, and said wall extending in a plane which extends in said direction and passes through said cradle, and away from a position occupied by said punch immediately prior to the crushing and bending.

8. A method according to claim 7, wherein said wall extends in said direction.

9. A method according to claim 7, wherein said punch and said die are so shaped that, simultaneously with the crushing and bending of said section, said section is formed with turned-back 10. A method according to claim 1, wherein said section is an intermediate section of said tube, and said part is placed in said die such that said part extends across a recess in said die and that said section lies substantially directly between said recess and said punch, and one of said die and said punch is moved one towards the other such that said punch penetrates said recess and in so doing displaces said section into a position against a suitably shaped wall of said recess and simultaneously therewith bends said remainder relatively to said section and crushes said section radially against said wall.

11. A method according to claim 10, wherein said wall of said recess is convex, and said punch has a concave face which crushes said section against said wall.

12. A method according to claim 10, wherein said part is placed in said die such that it has two end sections supported by respective cradles, said wall and said cradle extending in approximately the same direction as one another and transversely to the direction of movement of said one of said punch and said die towards the other.

said remainder.

16. A method according to claim 1, and preceded by inserting within said section a section of a second tube, the crushing and bending of the first-mentioned section being accompanied by corresponding crushing and bending of said section of said second tube.

17. A method according to claim 1, wherein said punchcomprises a rolling member arranged to roll on said section during the crushing and bending.

Claims

1. A method of crushing and bending a section of a tube comprising placing in a die of a press a part of said tube including said section, and moving one of said die and a punch of said press towards the other to crush one wall portion of said section inwardly towards a diametrically opposite wall portion of said section so that said section acquires a double-walled channel form extending along said section and to bend said section and the remainder of said part one relative to the other so that said remainder extends from the base of said channel in a direction away from the mouth of said channel.

3. A method according to claim 1, wherein after the crushing, each of said one wall portion and said opposite wall portion is of substantially constant cross-section throughout its length.

6. A method according to claim 5, wherein said face and said wall are each asymmetrical throughout their lengths with respect to a plane extending in said direction and containing the longitudinal axis of said part when placed in said die, whereby said section after crushing and bending has its longitudinal central plane oblique to that of said remainder.

7. A method according to claim 4, wherein said part is placed in said die such that it is supported by a cradle of said die, said cradle extending transverse to the direction of movement of said one of said punch and said die towards the other, and said wall extending in a plane which extends in said direction and passes through said cradle, and away from a position occupied by said punch immediately prior to the crushing and bending.

8. A method according to claim 7, wherein said wall extends in said direction.

9. A method according to claim 7, wherein said punch and said die are so shaped that, simultaneously with the crushing and bending of said section, said section is formed with turned-back

10. A method according to claim 1, wherein said section is an intermediate section of said tube, and said part is placed in said die such that said part extends across a recess in said die and that said section lies substantially directly between said recess and said punch, and one of said die and said punch is moved one towards the other such that said punch penetrates said recess and in so doing displaces said section into a position against a suitably shaped wall of said recess and simultaneously therewith bends said remainder relatively to said section and crushes said section radially against said wall.

13. A method according to claim 12, wherein said two end sections swing out of the cradles towards said punch during the crushing and bending.

14. A method according to claim 12, wherein said wall and said cradles extend perpendicularly to said direction of movement.

15. A method according to claim 1, wherein the crushing and bending of said section is accompanied by the crushing of one wall portion of said remainder inwardly towards a diametrically opposite wall portion of said remainder.

17. A method according to claim 1, wherein said punch comprises a rolling member arranged to roll on said section during the crushing and bending.