FIELD OF THE INVENTION

This invention relates to a pipe or tube bending machine and particularly to a pipe bending machine of the draw bending type.

BACKGROUND AND SUMMARY OF THE INVENTION

A draw bending machine comprises a bending die and a clamp for clamping the pipe to the bending die. The ^" bending die is turned under power about its axis and this movement of the bending die is transmitted to the clamp to rotate the clamp along with the bending die (or drive may be provided direct to an arm which mounts the clamp to rotate it with the bending die), and thus bend the pipe. The clamp is then released and the arm which carries it rotated back to its initial position. The pipe is gripped in a carriage which moves towards the bending die in order to advance the pipe and position it for each successive bend to be made, and the carriage also includes an arrange¬ ment for turning the pipe about its axis to a required orientation so as to select the plane in which the pipe will be bent each time. Known draw bending machines are not readily capable of bending to different radii or of accepting rectangular-section or oval-section tubing and bending it in different planes.

In accordance with this invention, there is provided a pipe bending machine of the draw bending type, having a bending die with different pipe-receiving profiles, a carriage for gripping, advancing and turning the pipe to be bent, and means for adjusting the position of the bend¬ ing die along its axis and/or for adjusting the axis on which the carriage grips the pipe.

The pipe bending machine preferably includes a com¬ puter numerical control system so that all the displace- ments within the machine, for effecting the successive bends in a given pipe, are carried out automatically and under numerical control, including any adjustments of the bending die along its axis (or of the axis on which the carriage grips the pipe), which adjustments can be carried out automatically between bends, so that successive bends in the same length of pipe can be carried out to e.g. different radii.

For example the bending die may be provided with a number of pipe-receiving profiles (preferably 3 or more) one above another (i.e. spaced along the vertical axis of the bending die) these profiles being of different radii and serving to bend the pipe to those different radii. In order to select the different profiles, in one embodi¬ ment the carriage is shifted vertically to align the pipe with the required profile of the bending die, and the carriage must also shift the axis of the gripped pipe sideways so that the pipe will align tangentially with the selected portion of the bending die: alternatively the bending die may be shifted vertically and the carriage serve to shift the axis of the gripped pipe side¬ ways. In another embodiment, the carriage holds the pipe

along a fixed axis and the bending head is displaceable both along its axis and sideways in order to select a different profile of the bending die for use.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this invention will now be described by way of examples only and wit-h reference to the accom¬ panying drawings, in which:

FIGURE 1 is a diagrammatic plan view of a draw bending machine in accordance with this invention;

FIGURE 2 is a diagrammatic section on the line II-II of the machine of Figure 1 , exaggerated in the vertical direction;

FIGURE 3 is a side view of a pipe-holding carriage of the machine of Figures 1 and 2;

FIGURE 4 is a diagrammatic plan view of the front end of a modified embodiment of machine; and

FIGURE 5 is a diagrammatic section through an alternative bending die and clamp arrangement, for handling pipes of rectangular or oval section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figures 1 and 2 of the drawings, there is shown a pipe bending machine of the draw bending type. The machine comprises a horizontal machine bed 9 mounting a bending head 10 at its forward end. This bending head comprises a bending die 12 of generally cylindrical form and mounted for rotation about its axis A, which is dis¬ posed vertically. The bending die 12 is formed with an annular groove 14 which is semi-circular in section, and is provided with a short, flat-faced, tangential extension 12_ which has a groove forming a tangential extension of the groove 14. A clamp block 16 is provided to co-operate with the bending die extension 12a_ and is formed with a semi-circular section groove 16a. across its face, so that it can clamp a pipe 1 against the bending die. The clamp block 16 is mounted to an arm 18 for sliding movement by an hydraulic actuator 17 towards and away from the bending die extension 12a_: the arm 18 is mounted for rotating about the axis A of the bending die 12 so that it will turn with the bending die during a bending operation.

The bending head 10 further comprises a pressure die 20 mounted to the machine bed 9 and having a flat front surface formed with a semi-circular section groove co¬ operating with the groove 14 of the bending die 12. This pressure die 20 is movable towards and away from the bending die by an hydraulic actuator 21, and is mounted so that it will move lengthwise of the pipe 1 during a bending operation. A wiper die 22 may also be provided, fixed to the machine bed 9, positioned opposite the pressure die 20 and shaped at its forward end to fit close to the bending die 12. The flat surface of the wiper die 22 which faces the pressure die 20 is formed with a semi¬ circular section groove co-operating with the groove of the pressure die 20.

The bending machine further comprises a pipe or tube holder 26 mounted to a carriage 24 which is mounted for sliding movement along the length of the machine bed 9 under the power of a motor 25 and via a drive belt 25a_ 5 for example. The pipe holder 26 comprises a cylindrical body through which, in use, the pipe 1 extends, and is provided with a collet 26a which can be applied to grip the pipe. The pipe holder body is rotatable about its axis and coupled to a drive motor 27 for effecting this

10 rotation.

The bending machine also comprises a mandrel 28 carried at the end of a mandrel rod 30, the mandrel being positioned in the pipe 1 to support the latter internally immediately upstream of the bend being formed, in use of

15. the machine. The mandrel rod is mounted by a holder 31 to the machine bed beyond the trailing end of the pipe being processed.

The machine is controlled by a computer numerical ^" control system 50. In use, with a pipe 1 over the mandrel

20 28 and mandrel rod 30 and held in the pipe holder 26, then firstly the control serves to advance the carriage 24 to position the pipe 1 correctly, relative to the bending head, ready for the first bend to be made in the pipe 1. Then the pressure die 20 is advanced to press the pipe against

25 the bending die ^" 12 and wiper die 22, and the clamping block is advanced to clamp the pipe 1 securely against the bending die extension 12a. Next the bending die 12 and clamp arm 18 are turned together around the axis A of the bending die (and through the angle required), for example by a drive

30 motor 45 applying power to a spindle 40 on which the bend¬ ing die 12 is mounted (Figure 2). During this step the pressure die 20 slides forwardly in following a displace¬ ment of the pipe 1 which occurs, in the region of the bend¬ ing head 10, as the bending die 12 turns. The clamp block

16 and the pressure die 20 are then retracted to free the pipe 1 from the bending die 12 and the clamp arm 18 is returned to its initial position by a drive motor 47 coupled to it, the clamp arm 18 being journalled about the spindle 40.

The carriage 24 is next advanced an appropriate amount so as to position the pipe 1 correctly for the next bend. The bending die 12 is returned to its initial position by its drive motor 45 and the pressure die 20 is also returned to its original position. If the next bend in the pipe 1 is to be effected in a different plane from the first bend, then the pipe holder 26 is turned through an appropriate angle. The next bend in the pipe 1 is then carried out in the same manner as described above, and the whole sequence of steps is repeated for •all the following bends which are to be made in the pipe 1.

The entire operation of the machine is under computer numerical control from the control system 50, including in particular the measured displacements of the carriage 24, pipe holder 26 and bending die 12 and the application/release movements of the clamp block 16 and pressure die 20. ^"

In addition to the structure and operation of the pipe bending machine of Figures 1 and 2 so far described, the bending die 12 has additional pipe-receiving profiles 13 spaced along the axis A and of different profiles to each other and from the profile 14, these profiles being on different radii and serving to bend a given pipe 1 to different radii. The clamp 16 is also .formed with additional profiles 15, so that it has different profiles to co-operate with the respective profiles of the bending die.

In the embodiment of Figures 1 to 3, the carriage is arranged so that the axis on which the pipe 1 is held may be adjusted both vertically and sideways (under computer numerical control) so as to align the pipe with any selected one of the profiles of the bending die, and align it tangentiaTly with the selected profile 14 or 13. For vertical adjustment, the carriage 24 mounts a platform 32 which is displaceable vertically by an electric motor 33 fixed to carriage 24 and driving a lead screw 34 engaged with the platform 32. For sideways adjustment, platform 32 mounts a second platform 35 displaceable sideways by an electric motor 36 fixed to platform 32 and driving a lead screw 37 engaged with the second platform 35: the pipe holder 26 is mounted on the second or upper platform 35. Also similar means are provided for moving the man¬ drel rod holder 31 • ^'

In a modified embodiment shown in Figure 4, the carriage (not shown) holds the pipe along a fixed axis _ (i.e. the arrangements for displacing the pipe holder vertically and sideways are dispensed with). Instead, the bending head, comprising the bending die 12, clamp arm 18, pressure die 20, wiper die 22 and structure 60 mounting these assemblies, is displaceable both in the horizontal direction H and the vertical direction. This modified embodiment is suited to the smaller machines, e.g. for pipes of 16mm outer diameter and smaller. These displacements are effected under computer numerical con¬ trol by the control system and a locking system is pre¬ ferably included to apply a lock automatically when the head is moved to a new position.

For the sideways displacement of the bending head, the structure 60, which mounts the bending die 12, clamp arm 18, pressure die 20 and wiper die 22, is displaceable

across a platform 62 by an electric motor 61 fixed to platform 62 and driving a lead screw 63 engaged with structure 60. For the vertical displacement, platform 62 is mounted slidably to the end of machine bed 9 and displaced by an electric motor 64 which is fixed to the machine bed and drives a lead screw 65 engaged with the platform 62.

In the machines which have been described, the bending head may include a bending die and/or clamp which is replaceable by a different component, e.g. for bending to a different set of radii or for receiving pipes of different outer diameters. The computer numerical control system of the machine is preferably arranged such that if data is entered identifying the particular component fitted (e.g. a single code number), the bending head (or the-carriage) is automatically displaced to -the correct positions both in the vertical and horizontal directions for each selected profile of the bending die. In use, the control system automatically carries out the required displacements in response to data identifying the profile of the bending die to be used. In particular, in executing a program for forming successive bends in a pipe, the con¬ trol system may automatically displace the bending head, or the carriage, between consecutive bends, so that the next bend will be formed to a different radius.

In the machines which have been described, the different bending die profiles may be suited to different pipe diameters (i.e. their semi-circular grooves are of different radii), or even of different shapes. The modification of bending die and clamp shown in Figure 5 is for handling pipes of rectangular or oval section, so that these may be bent in a plane parallel to their long sides or in a plane parallel to their short sides. Thus,

the bending die 12 has profiles 70,71 suited to these respective orientations and the clamp 16 has complementary profiles 72,73, the alternative orientations of the pipe being shown at 74,75.