FIELD OF THE INVENTION

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

BACKGROUND AND SUMMARY OF THE INVENTION

5 A draw bending machine comprising 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

10 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 is rotated back to its initial position. The clamp is applied and released by driven movement of it

15 towards and away from the bending die. Hitherto the dis¬ placement of the clamp has always been substantial, typically of the order of 80mm. However, in certain

instances, for example when bending a pipe to serpentine shape, this substantial displacement of the clamp creates restrictions on the product which may be formed, because it is necessary to avoid the pipe being positioned on the path which the clamp follows when it is released.

In accordance with this invention, there is provided a pipe or tube bending machine of the draw bending type, comprising a bending die, a clamp for clamping a pipe or tube to the bending die, means for displacing the clamp towards and away from the bending die to apply and release the clamp, and means for limiting the displace¬ ment of the clamp away from the bending die so that it is just sufficient for releasing the pipe or tube.

For example, the clamp may be limited to a displace- ment of say 1mm, which is just sufficient to release the clamped pipe or tube but places a minimal restriction on the permissible positioning of the pipework of the product being formed.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIGURE 1 is a diagrammatic plan view of an example of pipe bending machine of the draw bending type in accordance with this invention;

FIGURE 2 is a diagrammatic section on enlarged scale through the bending die and clamp arrangement of the machine of Figure 1 on the line II-II of Figure 1 ; FIGURE 3 is a similar section through a modified bending die and clamp arrangement; and

FIGURE 4 is a similar section through an alternative bending die and clamp arrangement.

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 12a_ 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 1βa_ 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 _, an ^" d 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_ 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 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 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 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 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 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.

Referring to Figures 1 and 2, when bending the pipe 1 to a serpentine form (for example) as shown, the dis¬ placement of the clamp block 16 is limited to prevent it being interfered with by the adjacent run of the pipe. A stop 60 (shown diagrammatically) is mounted to and pro¬ jects from the clamp arm 18 and limits the displacement of the clamp block 16, away from the bending die 12, to an amount (say 1mm) just sufficient to release the pipe 1. The hydraulic actuator 17 is coupled to a slide 62 and, on its forward stroke, the actuator 17 advances the slide 62, which carries an adjustable abutment 64 serving to engage

the rear of the clamp block and urge it against the bending die 12. On its reverse or releasing stroke, the actuator 17 displaces the slide 62 through its usual full travel (perhaps 80mm) and the clamp block 16 releases on its own: alternatively its release may be effected by a peg 66 (Figure 2) which is projected upwards from the slide 62 and positioned so as to act on the clamp block 16 in the last 1-5mm of the "clamp-off" stroke. The stop 60 limits the travel of the clamp block, as noted above. Preferably the stop 60 may be moved out of the way and the clamp block 16 fixed to the slide 62 when the normal full travel of the clamp block is required. The restricted-travel mode of the machine may be employed when forming a pipe to a shape other than the serpentine shape which is shown. In the modified arrangement shown in Figure 3 _> the actuator 17 for the clamp block 16 is mounted below the slide 62 and coupled to it by toggles 67,68 providing a lockable movement.

In the modified arrangement shown in Figure 4, the clamp block 16 is coupled to a lead screw 70 driven by an electric motor 72 under numerical control: the control may provide for a limited (e.g. 1 mm) displacement of the clamp block 16, or provide a greater displacement when, for other uses of the machine, this is required.