Mandrel Assembly for a Tube Bending Machine

This application claims priority to Italian Patent Application No. 102024000007831 filed Apr. 9, 2024, the contents of which is hereby incorporated by reference in its entirety.

The present invention relates to a mandrel assembly for a tube bending machine, comprising:

In tube bending machines, the use of mandrel assemblies is well known, as they serve the purpose of supporting the tube profile from the inside during the deformation process, so as to prevent the formation of wrinkles or ovalization of the tube.

A fundamental aspect is the formation of a substantial lubricant film in the gap between the mandrel assembly and the inner surface of the tube. Normally, the lubricant (which may have different viscosities) is pumped from a supply system on board the machine.

The supply system pumps the lubricant through the mandrel rod. The task of distributing the lubricant inside the tube is assigned to the lubricant outlet ports present on the mandrel body. In more demanding applications, the lubricant distributed by the ports is not sufficient; therefore, a manual pre-lubrication of the inside of the tube by the operator is required.

In conditions of poor lubrication, there is a risk of overheating of the components and malfunctioning of the process, with a possible rupture of the tube.

An object of the present invention is to provide a solution that allows for improved lubrication of the inside of the tube by the mandrel assembly.

This and other objects are fully achieved according to the present invention thanks to a mandrel assembly as described and claimed herein.

Advantageous embodiments of the present invention are described.

In summary, the present invention is based on the fact that the extreme distal articulation element comprises a deflector element fixed to the front side of the extreme distal articulation element, opposite the respective through-holes, the deflector element being configured to radially deflect outwardly the lubricant exiting the through-holes.

Thanks to such a mandrel assembly, it is possible to improve the distribution of the lubricant, as the lubricant exiting the mandrel body is able to pass through the space between the mandrel body and the extreme proximal articulation element, and through the spaces between successive articulation elements until it reaches the front side of the extreme distal articulation element, passing through the through-holes formed in the articulation elements.

In this way, the bending process becomes more reliable. Furthermore, the process becomes more repeatable, always ensuring the necessary amount of lubricant. Additionally, the process becomes safer by preventing breakages. Moreover, the process becomes more economical by avoiding waste. Finally, the process becomes more economical by eliminating the need for manual pre-lubrication.

Preferably, each articulation element includes a hinge portion through which each articulation element of the series of articulation elements is connected to an adjacent articulation element of the series of articulation elements, and a blanket portion attached to and arranged around the hinge portion, wherein the through-holes are entirely formed through the blanket portion.

According to an embodiment, the through-holes have a minimum diameter equal to or greater than 4 mm. Such a dimension is recommended when using high-viscosity lubricants, such as lubricant gels.

In, an example of a tube bending machine is schematically represented, in which a tube T is being processed. The tube bending machine comprises a die, which has on its lateral surface a groove with a curved path of a predetermined radius around a z-axis, perpendicular to the longitudinal axis of the tube T, a pair of clamping blocks, and a bending slidewhich is rotatable around the z-axis. Initially, the tube T is clamped between the clamping blocksand extends forward beyond the dieand the bending slide. Subsequently, with the tube T clamped not only between the clamping blocks, but also between the dieand the bending slide, the bending slideis rotated around the z-axis, thus wrapping the tube T around the dieand generating in the tube a bend with a mean radius substantially corresponding to the mean radius of the groove of the die.

It is understood that the machine described above is provided solely by way of non-limiting example, as the present invention may be applied to different types of tube bending machines.

The tube bending machine comprises a mandrel assembly, globally denoted by, configured to be inserted inside the tube T and to support the tube profile from the inside during the bending process.

The mandrel assemblycomprises a mandrel bodyconfigured to be inserted inside the tube T. The mandrel bodycomprises a proximal endand a distal end, and is laterally delimited by a peripheral surface, which is opposed to an internal surface of the tube T. For the purposes of the present description, the terms “proximal” and “distal” respectively indicate “closer” and “farther” with respect to a control system A of the mandrel assembly, schematically represented in.

The mandrel assemblyfurther comprises a mandrel rodrigidly connected to the proximal endof the mandrel bodyand configured to support and move the mandrel body. To this end, the mandrel rodis supported by the control system A onboard the machine, which is operable to move the rod along the longitudinal axis of the tube T.

The mandrel assemblyfurther comprises a series of articulation elements,,arranged at the distal endof the mandrel body, which are articulately connected to one another and to the mandrel body. The articulation elements,,, commonly known as “balls”, thanks to their articulated connections, are capable of following the deformation of the tube T during the bending process, providing support to the wall of the tube T. In the illustrated example, there are three articulation elements; however, it is understood that the number of articulation elements may vary, for example, it may be two or more than three. Each articulation element of the series of articulation elements-is connected to an adjacent articulation element of the series of articulation elements-through a respective cylindrical or spherical hinge,. The extreme proximal articulation elementof the series of articulation elements-is also connected to the distal endof the mandrel bodythrough a cylindrical or spherical hinge.

More precisely, each articulation element-comprises a central portion-through which each articulation element-is connected to an adjacent articulation element-(forming the hingesand), and a blanket portion-attached to and arranged around the central portion-. The central portionof the extreme proximal articulation elementis also connected to a central insertfixed to the mandrel bodyat the distal end, forming the hinge. Advantageously, the blanket portions-may be made of a different material from the central portions-. For example, the blanket portions-may be made of a material with a lower friction coefficient compared to the material of the tube.

The control system of the mandrel assemblyincludes a lubricant supply system B, configured to supply a lubricant, such as a lubricant gel, to the mandrel assembly, and to lubricate the surfaces of the mandrel assemblyin contact with the interior of the tube T. To this end, the lubricant supply system B includes a pump connected to a lubricant feed passageformed along the mandrel rod.

A network of lubricant transport channels is formed through the mandrel body, communicating with the lubricant feed passage, as shown in.

In the illustrated example, the network of channels comprises a central manifoldformed centrally in the mandrel bodyand directly communicating with the lubricant feed passage. From the central manifold, a plurality of radial channelsextend radially toward the peripheral surfaceof the mandrel body. From each of the radial channels, a respective longitudinal channelextends longitudinally toward the distal endof the mandrel body and opens to the exterior of the mandrel bodyat the distal end, through a respective lubricant outlet port. Additionally, the radial channelsopen to the exterior of the mandrel bodyat the peripheral surface, with respective lubricant outlet ports. The lubricant outlet portsopen into at least one surface grooveformed on the peripheral surfaceof the mandrel body. In the illustrated example, the surface grooveis part of a network of surface grooves formed on the peripheral surfaceof the mandrel body. Some grooves of the network extend in the circumferential direction, while others extend in the longitudinal direction of the peripheral surface.

A plurality of through-holesis formed through each of the articulation elements-, extending along the longitudinal direction of the respective articulation element-. The through-holesare configured to convey lubricant to the front side of the extreme distal articulation elementof the series of articulation elements-.

More precisely, the through-holesare entirely formed through the blanket portion-of each articulation element-. In other words, each through-holeis entirely surrounded by the blanket portion-and does not border the central portion-. In this way, the through-holescan be manufactured in a very simple manner.

The through-holesmay have a minimum diameter equal to or greater than 4 mm. Such a dimension is recommended when using high-viscosity lubricants, such as lubricant gels. However, it is understood that the present invention is not limited to this type of lubricant, and that it is possible to use lower viscosity lubricants, such as oils, and therefore, the through-holes of the articulation elements may have smaller diameters.

Advantageously, the extreme distal articulation elementcomprises a deflector elementfixed to the front side of the extreme distal articulation element, and including a revolution surfacewith a curved profile arranged opposite the respective through-holes. The deflector elementis configured to radially deflect outwardly the lubricant exiting the through-holesof the extreme distal articulation element. This feature improves the distribution of the lubricant on the internal surface of the tube T.