Bending Machine

The present invention relates to a bending machine for use in bending pipes such as oil pipes and iron bars and the like. More particularly, the invention relates to a bending machine comprising a feed mechanism mounted on a base block for advancing a length of workpiece to a bending section, and a bending assembly including a plurality of rotatable bend dies arranged along a common rotational axis and a plurality of clamp dies movable toward and away from the bend dies, the bend dies and the claim dies being adapted to hold the workpiece therebetween and bend the workpiece by rotating in unison about the rotational axis.

A bending machine as described above which comprises a bending assembly including a plurality of bend dies arranged along a common rotational axis is capable of bending elongate workpieces having varied diameters and bending such workpieces to varied curvatures by selecting suitable bend dies. In order to achieve this, however, the bending assembly and the workpiece must be movable relative to each other in directions on a bending plane of the workpiece and in directions along the rotational axis of the bend dies. According to a known construction, a first actuator for effecting the movements on the bending plane and a second actuator for effecting the movements along the rotational axis of the bend dies are both mounted on the base block. More particularly, the two actuators are provided between the feed mechanism and the base block to move the workpiece on the bending plane and along the rotational axis of the bend dies. However, where the movements on the bending plane is effected by means of the feed mechanism supporting the elongate workpiece, the positional adjustment of the workpiece tends to lack in precision although the movements along the rotational axis may be effected with no problem. Such precision cannot be assured because it is an attempt to control the position of a part of the elongate workpiece adjacent a leading end thereof by moving the feed mechanism which is holding a part of the elongate workpiece adjacent a tail end thereof. A bending operation to bend the workpiece by rotating the bending assembly without accurate positioning of the workpiece in the direction on the bending plane, would result in failure to achieve a desired bend angle.

As a solution to this problem a construction has been proposed as in Japanese Patent Publication No. 59-32410, for example. According to the proposed construction, the first and second actuators are both provided between the bending assembly and the base block. More particularly, a frame carrying the bending assembly is attached to the base block to be movable on the bending plane, and the first actuator is provided between this frame and the base block while the second actuator is provided between the frame and the bending assembly. This construction has the advantage of assuring accurate positioning of the workpiece on the bending plane since the bending assembly is moved on the bending plane. However, the second actuator must be moved together with the bending machine and therefore the devices to be moved are heavy, which gives rise to a new problem of lacking in speedy movement and hence poor working efficiency.

This invention has been made having regard to the above noted disadvantages of the prior art, and its object is to provide a bending machine having practical utility and capable of bending elongate workpieces to desired angles efficiently.

In order to achieve this object, a bending machine according to this invention is characterized in that the bending assembly is attached to the base block to be movable on a bending plane of the workpiece, a first actuator being provided between the bending assembly and the base block for moving the bending assembly on the bending plane, and the feed means is mounted on the base block to be movable in directions along the rotational axis of the bend dies, a second actuator being provided between the feed mechanism and the base block for moving the feed mechanism along the rotational axis of the bend dies.

Thus, the relative movements between the bending assembly and the workpiece on the bending plane are effected by moving the bending assembly, which assures accurate positioning of the workpiece on the bending plane. On the other hand, the relative movements along the rotational axis of the bend dies are effected by moving the feed mechanism, which permits the devices moved on the bending plane to be lightweight. As a result, the elongate workpiece such as a length of pipe may be bent to a desired angle efficiently.

Other features and advantages of this invention will be apparent from the following description.

The drawings illustrate a bending machine embodying this invention, in which:

FIG. 1 is a side view of the bending machine,

FIG. 2 is a plan view of the bending machine,

FIG. 3 is a plan view of a principal portion of the bending machine, and

FIGS. 4a, 4b and 4c are front views of the principal portion in varied stages of operation.

Referring to FIGS. 1 and 2, the bending machine shown therein comprises a base block 1 resting on a floor and a feed mechanism 2 mounted thereon for advancing a pipe P, which is an example of a length of workpiece to be bent, maintained in a horizontal posture to a bending section of the machine. The feed mechanism 2 includes a carriage 3 movable axially of the pipe P, a servomotor 5 for moving the carriage 3 by means of a chain 4, a mandrel 6 for supporting the pipe P by relatively rotatably fitting thereinto, a hydraulic cylinder 7 for moving the mandrel 6 axially of the pipe P. The carriage 3 carries a chuck 8 for receiving and holding an intermediate portion of the pipe P, a hydraulic cylinder 9 for switching the chuck 8 between a position to hold the pipe P and a position to release the pipe P, and a DC servomotor 10 for rotating the chuck 8 about the axis of the pipe P. The feed mechanism 2 in its entirety is mounted on the base block 1 to be vertically movable relative thereto. The feed mechanism 2 is forcibly moved up and down by a second actuator 11 comprising two hydraulic cylinders 11 provided between the feed mechanism 2 and the base block 1. One of the cylinders 11a is provided between the mandrel 6 and the base block 1 and the other 11b is provided between the carriage 3 and a combination of chuck 8 and DC servomotor 10. By an associated action of the cylinders 11a and 11b the feed mechanism 2 in its entirety is moved up and down.

The machine further comprises a frame 13 carrying a bending assembly 12 mounted on the base block 1 at a side opposite the side at which the mandrel 6 is mounted. The frame 13 and bending assembly 12 are forcibly movable horizontally relative to the base block 1 by a first actuator comprising a DC servomotor 14 provided between the bending assembly 12 and the base block 1. More particularly, as shown in FIG. 3, the servomotor 14 is fixed to the base block 1 and a ball nut 16 in mesh with a screw shaft 15 rotatable by the servomotor 14 is attached to the frame 13, so that the bending assembly 12 and the frame 13 are horizontally slidable in unison by rotations of the servomotor 14.

Referring to FIGS. 3 and 4, the frame 13 rotatably supports a vertical shaft 17 which in turn supports a swing frame 18 fixed thereto. The shaft 17 and swing frame 18 are swingable in unison relative to the frame 13 by action of a hydraulic motor 19. An encoder 20 is attached to the frame 13 to detect swing angles of the swing frame 18, namely bend angles of the pipe P. Two bend dies 21a and 21b are removably secured to the shaft 17 one on top of the other. These bend dies 21a and 21b are interchangeable with other bend dies as desired to enable bending of pipes having varied diameters and to enable the pipe P to be bent to varied curvatures. The swing frame 18 supports a carrier 22 mounted thereon by means of a link mechanism (not shown) to be movable toward and away from the bend dies 21a and 21b. Two clamp dies 23a and 23b are removably secured to the carrier 22 one on top of the other. A hydraulic cylinder 24 is provided to cause the bend dies 21a and 21 b and clamp dies 23a and 23b to hold the pipe P therebetween and release the pipe P. The frame 18 carries a stationary frame 25 secured to a position closer to the base block 1 than is the swing frame 18. The stationary frame 25 supports a carrier 26 having the same function as the carrier 22. Two pressure dies 27a and 27b are removably secured to the carrier 26 one on top of the other to be operable by action of a hydraulic cylinder 28 to press the pipe P against the bend dies 21a and 21b. When the swing frame 18 is caused to swing with the bend die 21a or 21b and clamp die 23a or 23b holding the pipe P therebetween, these dies are rotated together through a desired angle about a rotational axis a of the shaft 17 whereby the pipe P is bent while being caused to slide relative to the pressure dies 27a and 27b. Thus, the bend dies 21a and 21b and clamp dies 23a and 23b constitute the bending assembly 12. Numbers 29 and 30 in the drawings denote screws for adjusting operative positions of the clamp dies 23a and 23b and pressure dies 27a and 27b according to a diameter of the pipe P and other conditions, respectively.

It will be understood that varied types of pipe having different diameters may be bent to desired curvatures by changing the bend dies 21a and 21b, as appropriate and deciding which should be placed on top of which. Relative movements between the bending assembly 12 and the pipe P in horizontal directions, namely in directions on a plane of pipe bending, are effected by the first actuator 14 disposed adjacent the bending assembly 12. This enables the position of pipe P relative to the bend dies 21a and 21b to be determined accurately for the achievement of high precision bending. Where a servomotor is employed as the first actuator 14 as described, its operation may be stopped at a desired position accurately and promptly, which contributes toward a high precision and speedy bending operation. Relative movements between the bending assembly 12 and the pipe P in vertical directions, namely in directions parallel to the rotational axis a of the bend dies 21a and 21b, are effected by the second actuator 11 disposed on the base block 1. This arrangement permits the mechanism for causing the horizontal relative movements to be lightweight to expedite the bending operation, as described in the introductory part of this specification.