GB1603010A - Metal pipe bending machine - Google Patents

Description

(54) METAL PIPE BENDING MACHINE (71) We, METALLURGICA BERGA MASCA S.p.A., a Joint Stock Company, organized and existing under the laws of Italy, of Via Dante Alighieri, 12, Mapello (Province of Bergamo), Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a metal pipe bending machine, and specifically to a machine for forming elbows from pipes of fairly large diameters.

Conventional tube or pipe benders comprise a grooved roller guide and a local heating system, both of which are stationary, a pusher operative to advance a pipe section or length through the guide and heater, and a bending arm which is journalled and forces the pipe section mouth to travel along an arc of a circle. This system is generally satisfactory, but frequently causes bothersome failures in operation, which reflect in more or less serious manufacturing faults. Such faults are well known to the expert, and include lack of uniformity in the curvature, as well as excessive stretching and drafting, or thickness reduction, along the outer surface of the bend, and upsetting, with puckering or pleat formation along the inner surface of the bend or intrados. The prime causes of these faults, assuming that all the parameters have been correctly adjusted, are to be found in lack of uniformity of the pipe stock and of the material it is made of.

Such disuniformity, even if well within the tolerance limits, produces spot heating which, in turns. aggravates the lack of structural uniformity.

Careful investigation by the applicant has revealed that heating is, either directly or indirectly. a primary cause of most manufacturing faults to be found in pipe elbows.

Considerable effort has been devoted to securing a more accurate adjustment capability as regards temperature, by monitoring it through thermocouples located at several points, but the results have been inferior to expectation. Recently conducted investigations have led to the conclusion that not only the temperature is critical, but also the extent of the heated area. While the heated area had been suitably reduced, attention has been devoted to a more accurate control of the temperature by removing heat at a certain distance from the hot spot, such as to produce, additionally to a desired temperature level, also a predetermined temperature gradient. Although this approach did afford some improvement, the cited faults failed to be eliminated altogether. The idea behind temperature control was one of maintaining the heated area within the minimum value required, and of controlling through the thermal gradient the extension or spread of the hot and plastically deformable area; this latter type of control proved impossible to achieve with the desired accuracy as required.

In view of the above situation, it is a general object of this invention to eliminate or reduce substantially the faults of the prior pipe bending art.

A particular object of the invention is to provide a pipe bending machine for manufacturing metal pipe elbows, which affords smooth bending of the pipes without leading to an increase of the production costs, possibly while ensuring a higher output over the prior art systems.

These and other objects, such as will be apparent hereinafter, are all achieved, according to this invention, by a pipe bending machine characterized in that it comprises a stationary base, a supporting surface for a pipe to be bent on said stationary base, a fluid-operated actuator mounted on said stationary base, a carriage movable on said stationary base and operated by said actuator, a roller guide for the pipe on said carriage, a heating and cooling unit acting on a narrow area of said pipe at the exit from said roller guide, and a clamp-carrying arm for bending the pipe, journalled to said carriage.

Before describing the instant equipment in any detail, it is considered appropriate to provide here a simple and functional explanation of the invention essence. The instant machine separates in a far neater way the hot plastic area of the pipe from the rigid area thereof, while concurrently greatly reducing this deformation area. Assuming that the pipe is advanced in a relative direction at the same rate as in a conventional process, the radius of curvature being also the same, the bend involves now a smaller section and lasts less in that section. The ideal, as will be apparent, would be that of deforming infinitesimal sections at successive times, also infinitesimal. The length deformed each time could thus be hotter, and accordingly more plastic, it being better guided and therefore less likely to undergo irregular deformation by virtue of its shorter length. With such a provision, the presence of an area opposing little mechanical resistance relieves the transition areas of deformations, which were critical and an important source of faults.

To make the invention features and advantages better understood, a presently preferred embodiment thereof will be next described by way of example, and illustrated in the accompanying drawings, where: Figure 1 is a top plan view of a machine according to this invention; Figures 2 and 3 are similar views, at different operational stages of the machine; Figure 4 shows a section taken along the line IVIV of Figure 3; and Figure 5 is a sectional view taken along the line V-V of Figure 3.

A pipe bending machine according to the invention is generally indicated at 1, and will be discussed with reference to all of the drawing figures. It comprises a rigid stationary base 2 whereto are attached two parallel guides 3, each guide including a runway 4 and a rack 5, mutually associated. On the runways 4 travel idle wheels 6, while on the racks 5 mesh gear wheels 7, also mounted idle, which serve to provide precision guiding and are non-driving. The wheels 6 and gear wheels 7, in two pairs each, support a carriage 8 whereto all of the machine movable parts are connected. The carriage includes two longitudinal or side members 9 which are united together by two axle shafts 10 carried by the gear wheels 7 and by two crossmembers 11. The idle wheels 6 are mounted on stub shafts 12 projecting from the side members 9. The carriage is driven by two rods 13 of two fluid-operated cylinders 14, arranged parallel to each other and rigid with the base 2 or, if preferred, by a hydraulic motor.

A roller guide 15 is installed on the carriage for advancing relative to the pipe to be bent, known per se, as is a heating and cooling unit 16 which will be described more in detail hereinafter. To the carriage there is connected, by means of a vertical axis hinge pin 17 mounted to the frame 8, a swing or oscillating arm 18 equipped with a clamp 19 adapted to clamp against the arm the mouth of a pipe 20 to be bent. That pin will be necessarily located with its axis in the midplane of the heat-applying area. The pipe 20 is retained at its trailing end by a rear clamping member 21 which serves to lock the linear portion of the tube securely.

The heating and cooling unit constitutes the core of this invention, although it is not limited to the embodiment shown herein. It comprises a heating device 23, consisting of a toric ring header. also indicated at 23, and of plural centripetally arranged radial burners 24, each directing a fine flame cone onto the pipe circumference, which flame cones are adjusted to be equal to one another and uniformly distributed. The header 23 is fed with a combustible gas, such as plant gas, methane, acetylene, LP gas, and the like.

Adjustment is made, of preference, automatic, under control by a thermal probe, e.g.

a sliding contact thermocouple inside the pipe at the hot area, not shown. The unit 16 further comprises a cooling device, schematically represented by two rings 25 coaxial to the pipe 20 and arranged symmetrically with respect to the plane including the burners or nozzles 24. Such rings are effective to emit, as the case may be, either jets of cold air, or of a refrigerating gas such as CO2, or of cooling water, quenching oil, or other cooling liquid.

A shield or screen will be suitably placed between the heating and cooling areas. The choice of the coolant will be dependent on the qualities of the steel or metal of which the pipe is made. The gap or distance will be adjusted by trial and error; as the cooler is brought much nearer the heater, the fuel consumption will increase somewhat, thereby it will be better not to reduce such a distance farther than necessary to eliminate bending faults. It has been found that by restricting the hot and plastic area the temperature level becomes less critical, in that even a reasonably excessive temperature causes no failure.

In the light of the above description of the process and machine construction, the operation thereof will be evident. Initially, the carriage is moved away from the cylinders and supporting surface, as shown in Figure 1.

A pipe section or length is then inserted between the roller guide 15 to be retained in the clamp 21; the other pipe end being held in the clamp 19 of the arm 18. Upon reaching the proper temperature, the carriage 8 is pulled by the rods of the cylinders 14 toward the clamp 21, thereby the guide 15 and the heater 23 are caused to advance along the pipe 20, as shown by the arrows. The arm 18, being urged by the pipe, is caused to pivot and bend the pipe, as shown in Figures 2 and 3.

Actual tests have confirmed the process principles set forth, affording perfect elbows free of the usual faults, as well as an increased output, and increased rate of advance, which is now limited in practice only by the rate of pipe heating, in turn also dependent on the pipe thickness. Adaptation to different bends and radii of curvature is effected as in conventional machines.

The instant machine may be modified without departing from the invention scope.

Thus, for example, heating may be by induction, preferably at a high frequency to better spot the heat application. The arm 18, since the force F it opposes varies during the bending operation, could be friction braked in an adjustable manner. Alternatively, said arm could be rack pivoted by the carriage movement, to automatically ensure uniform stretching and upsetting all along its travel path. Furthermore, the clamp 19, heating and cooling unit 16, roller guide 15, and clamp 21, may be displaced transversely to vary the radius of curvature at will.

It should be added to the above considerations, that the inventive machine affords the formation of 180 bends in a pipe, in practice by forming two 90 bends in succession.

Thus, it has been shown that the correct way has been discovered to solve the problems connected with a good pipe bending technique, as contemplated in the invention objects.

WHAT WE CLAIM IS: 1. A pipe bending machine, characterized in that it comprises a stationary base, a supporting surface for a pipe to be bent on said stationary base, a fluid-operated actuator mounted on said stationary base, a carriage movable on said stationary base and operated by said actuator, a roller guide for the pipe on said carriage, a heating and cooling unit acting on a narrow area of said pipe at the exit from said roller guide, and a clamp-carrying arm for bending the pipe, journalled to said carriage.

2. A machine according to Claim 1, characterized in that said heating and cooling unit comprises an annular distributing header for combustible gas or mixtures, burners extending spider-like from said annular header to direct narrow flames onto a circumference of the pipe, and two rings arranged symmetrically with respect to the plane including said burners, adjacently the edges of the heated area, said rings directing circumferential jets of a cooling fluid onto said pipe.

3. A machine according to Claim 1, characterized in that said pipe bending arm is provided with friction braking means.

4. A machine according to Claim 1, characterized in that said pipe bending arm is caused to pivot by the carriage advance movement.

5. A machine according to Claim I, characterized in that it comprises two guides on said base having each a runway and a rack, whereon said carriage is movable with the interposition of idle wheels and idle gear wheels, respectively.

6. A pipe bending machine, as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. increased output, and increased rate of advance, which is now limited in practice only by the rate of pipe heating, in turn also dependent on the pipe thickness. Adaptation to different bends and radii of curvature is effected as in conventional machines. The instant machine may be modified without departing from the invention scope. Thus, for example, heating may be by induction, preferably at a high frequency to better spot the heat application. The arm 18, since the force F it opposes varies during the bending operation, could be friction braked in an adjustable manner. Alternatively, said arm could be rack pivoted by the carriage movement, to automatically ensure uniform stretching and upsetting all along its travel path. Furthermore, the clamp 19, heating and cooling unit 16, roller guide 15, and clamp 21, may be displaced transversely to vary the radius of curvature at will. It should be added to the above considerations, that the inventive machine affords the formation of 180 bends in a pipe, in practice by forming two 90 bends in succession. Thus, it has been shown that the correct way has been discovered to solve the problems connected with a good pipe bending technique, as contemplated in the invention objects. WHAT WE CLAIM IS:

1. A pipe bending machine, characterized in that it comprises a stationary base, a supporting surface for a pipe to be bent on said stationary base, a fluid-operated actuator mounted on said stationary base, a carriage movable on said stationary base and operated by said actuator, a roller guide for the pipe on said carriage, a heating and cooling unit acting on a narrow area of said pipe at the exit from said roller guide, and a clamp-carrying arm for bending the pipe, journalled to said carriage.

2. A machine according to Claim 1, characterized in that said heating and cooling unit comprises an annular distributing header for combustible gas or mixtures, burners extending spider-like from said annular header to direct narrow flames onto a circumference of the pipe, and two rings arranged symmetrically with respect to the plane including said burners, adjacently the edges of the heated area, said rings directing circumferential jets of a cooling fluid onto said pipe.

3. A machine according to Claim 1, characterized in that said pipe bending arm is provided with friction braking means.

4. A machine according to Claim 1, characterized in that said pipe bending arm is caused to pivot by the carriage advance movement.

5. A machine according to Claim I, characterized in that it comprises two guides on said base having each a runway and a rack, whereon said carriage is movable with the interposition of idle wheels and idle gear wheels, respectively.

6. A pipe bending machine, as hereinbefore described with reference to and as illustrated in the accompanying drawings.