RU2775766C1 - Mandrel for bending thin-walled rectangular waveguides - Google Patents

Abstract

FIELD: metal forming.

SUBSTANCE: invention relates to the field of metal forming and can be used for bending thin-walled rectangular waveguides of spacecraft. The mandrel contains a set of flexible elements assembled in a package made with the possibility of filling the inner cavity of the waveguide. Flexible elements are made in the form of square bars in cross section made of a porous composite material, the structure of which includes materials with a lubricating effect. The mandrel is equipped with metal mounting elements located at both ends of the mandrel for installing and removing it from the waveguide.

EFFECT: invention makes it possible to perform bending in two planes in one installation.

1 cl, 6 dwg

Description

The invention relates to various fields of industry, primarily rocket and space, aviation. In particular, the invention relates to the field of metal forming and can be used for bending thin-walled rectangular spacecraft waveguides.

It is known that space communication satellites contain a large number of rectangular waveguides, often having a complex spatial shape, for example, bends in different planes, as well as twisted zones. Spacecraft waveguides have flanges or couplings on both sides for fastening to each other and to other elements of waveguide technology. The length of individual fragments of waveguides is determined by technological limitations in the manufacture of waveguides of complex shape. With a complex shape, the presence of bends, it is necessary to use short sections of waveguides, connecting them together. This leads to an increase in the total mass of the waveguide path due to the large number of flanges and couplings. The waveguides used must have the constancy of the internal dimensions of the section and high quality of the inner surface. Existing technologies for bending waveguides impose restrictions on the length of individual fragments of waveguide paths. For aerospace engineering, an urgent task is to reduce the weight (mass) of waveguide paths through the use of thinner-walled waveguides. The use of thin-walled waveguides with a wall thickness of less than 0.65 mm encounters a number of technological difficulties. First of all, this is the problem of bending thin-walled rectangular waveguides without disturbing the geometry of the inner surface. Bending of pipes of rectangular section is a complex technological process due to the frequent loss of stability of the side (in the bending plane) elements of the pipe. The main defects that occur during the bending process:

- thinning with destruction of the waveguide wall along a larger bending radius;

- increase in the thickness and corrugation of the wall (local buckling) of the inner side along the small bending radius of the waveguide;

- distortion of the cross section of the waveguide in the bending zone.

At present, the theory and technology of bending round tubes is the most developed. Despite the wide scope of rectangular pipes, thin-walled pipes, as a structural material, are a little-studied element. Bending or twisting of a waveguide tube is a very complicated operation, since it requires expensive equipment, special skills and equipment. The main methods for bending a waveguide tube are the use of a high-precision bending machine, which is used with special calibrating internal equipment (inserted inside the waveguide tube), or the use of a machine with stepwise notching of the outer surface of the tube and simultaneous bending (also used with internal equipment).

The well-known basic waveguide bending technology used is bending in a pipe bender with three rollers or by means of a rotating cam, with a filler placed inside the waveguide.

The choice of filler for the waveguide tube plays a significant role in the bending process. It must provide the necessary rigidity and at the same time be plastic. It should be easy to install and remove without creating scratches on the inner surface of the waveguide.

From the existing prior art devices for bending products with a closed profile, in particular pipes, are known, which can be conditionally divided into two groups.

The first group includes devices that include an elastic filler placed inside the waveguide.

For example, there is a method for bending pipes (patent RU No. 2201308 C2, 2003) with a filler in the form of a flexible mandrel, which includes introducing a flexible mandrel into the pipe, and flexible rods with wedges and split rings are used as elements of the flexible mandrel for pressure control.

In the general case, in known similar methods (SU No. 386695, 1973; SU No. 963608, 1982; SU No. 1299651, 1987; RU No. 1552449, 1995; RU No. 2094151, 1997; US No. 3841138, 1974; US No. 6389872, 2002) , in preparation for the process of bending hollow products, a filler made of a solid elastic material is placed inside the workpiece, while the filler is identical in shape and size to the shape and dimensions of the internal cavity of the workpiece.

A common disadvantage of the above methods of the first group are:

- the difficulty of preparatory operations for installing the filler in the cavity of the product blank and extracting it through the entire length of the waveguide from the place of bending, especially if it is necessary to perform several bends in the waveguide, since the presence of friction during the introduction and removal of the filler on the inner surface of the product leads to deformation and local defects the inner surface of the waveguide;

- conflicting requirements for the properties of the filler - the need for sufficient hardness to prevent the formation of corrugations, a low coefficient of friction, and elasticity - from the condition of excluding the formation of a thin-walled rectangular pipe.

The second group of methods includes methods using bending mandrels-metal structures placed inside the workpiece.

So, for example, a design of a mandrel for bending pipes is known (AS SU 664714), containing a set of hinged links and an adjusting mechanism, in which, in order to allow bending pipes of various diameters, the mandrel links are made in the form of two levers with ball segment heads mounted on an axis with the possibility of rotation in the pipe bending plane, equipped with trunnions and pivotally connected to each other by bars with holes associated with the adjusting mechanism, while the trunnions are installed in the said holes.

The main disadvantage of similar solutions of the second group (RU 2242314, SU 1706747, SU 386695, etc.) is the impossibility of their application for the manufacture of waveguides of complex shape from thin-walled pipes. The operations of inserting into the blank cavity and extracting mandrels-metal structures after bending, especially if there are several bends in the product, unequivocally lead to deformation of the thin walls of the pipe and to local defects in the inner surface of the waveguide. The mandrel designs by which these methods are carried out are costly, labor-intensive due to the complexity of mounting, adjusting and removing the mandrel.

For the prototype of the device, the technical solution closest to the declared one was chosen (Bushminsky I.P. Manufacturing of microwave structural elements. Waveguides and waveguide devices / I.P. Bushminsky - M.: Higher school, 1974, p. 12-15), in in which the device for bending waveguides is presented in the form of steel plates, which fill the internal cavity of the waveguide. A set of rectangular spring steel plates with a thickness of 0.1-0.3 mm is used . Plates with a width equal to the internal dimension of the workpiece, along which the bend is made (along a narrow or wide wall), and a length exceeding the length of the workpiece by 1.5 times, are collected in two packages, the total thickness of which is 2-4 mm less than necessary for filling the entire volume of the waveguide. Both packages are generously lubricated and installed in the waveguide pipe, a press-span gasket is also placed there to protect the side walls. Filling the cavity with steel plates - ensures the stability of the internal dimensions of the section of the waveguide pipe. After bending, the wedge is pulled out and the packs are removed.

The disadvantages of the prototype are low functionality and manufacturability associated with the inconvenience of operations: bending is performed on one size of the workpiece (on a narrow or wide wall), i.e. to perform a bend in two planes, a second set of plates is required along the width of the bend, and an additional disadvantage is the possibility of forming scratches on the inner surface when inserting and removing steel plates, and the complexity of installing gaskets to protect the walls. These disadvantages are especially manifested when thin-walled waveguides are used. In addition, the disadvantage is the use of a large amount of lubricant, due to the relatively high coefficient of friction of the materials used.

For the claimed invention, the following essential features common with the prototype have been identified: a mandrel for bending rectangular waveguides in the form of a set of flexible elements assembled in a package that fills the internal cavity of the waveguide.

The technical problem of the proposed invention is the creation of an easy-to-use tooling - a mandrel for bending thin-walled rectangular waveguides, which allows bending in two planes in one installation, meeting modern requirements for functionality, manufacturability, productivity, durability and quality of the resulting inner surface of the waveguide.

This problem is solved by the device proposed by this invention - a mandrel, consisting of a set of bars square in cross section, having the shape of a wedge, at least on one side, also having metal fastening elements with holes at the ends of the mandrel (for installation and removal - pulling the mandrel by the fastening element from the side of the wedge when installing into the waveguide and facilitating extraction by pulling using a hole in the fastening element at the wide end of the mandrel at the end of the bending operation), and the rods are made of composite materials that have materials with a low coefficient of friction in their structure (for example, graphite, fluoroplastic, etc.), that is, they have a lubricating effect, equally well bending in two planes (on the narrow or wide side) and porous in structure (to hold the lubricating layer). The wedge, consisting of individual bars, when moving in the direction of decreasing section reduces adhesion to the part in both planes of the part (unlike the prototype). The mandrel can be made in the form of a set consisting of a central bar - a wedge of variable section and a set of side bars located along the perimeter of the wedge, in the general set corresponding in shape to the inner section of the bent waveguide and made to fit with a gap

The technical result of the claimed invention is the expansion of the technological capabilities of bending thin-walled waveguides of complex shape with bending, for example, in two planes, and as a result of reducing the number of flanged connections of waveguide paths and improving the quality of the inner surface of the waveguides in the places of bending. The proposed design also has an advantage in terms of unification and interchangeability: mandrels for waveguides of various sections can be assembled from the same elements - bars calibrated according to the section.

The essence of the invention is illustrated by drawings:

- General view of the mandrel device in Fig.1;

- cross-section of the mandrel in Fig.2;

- General view of the mandrel, threaded through the blank-waveguide in Fig.3;

- General views in two planes of the waveguide after bending using a mandrel in Fig.4;

- General views of the mandrel according to claim 2 of the claims in figure 5;

- cross-section of the mandrel according to claim 2 of the claims in Fig.6.

2. Mandrel according to claim 1, characterized in that the set of rods consists of a central rod - a wedge of variable section and a set of side rods located along the perimeter of the wedge, in the general set corresponding in shape to the internal section of the bent waveguide.

Figure 1 shows the general views of the mandrel (1) for bending thin-walled waveguides of rectangular cross section, made in the form of a set of square bars (2) made of a composite material with low friction and porous in structure. The mandrel also contains at both its ends metal fastening elements (3), (4) with technological holes for installing and removing the mandrel from the waveguide (5).

Figure 2 shows the cross-section of the mandrel (1) - a set of square bars (2), corresponding in the set to the shape of the inner section of the bent waveguide (5).

Figure 3 shows a General view of the mandrel (1) threaded from the narrow side of the wedge - from the fastening element (3) through the workpiece - the waveguide (5).

Figure 4 shows the general views of the waveguide (5) after bending in two planes using a mandrel (1).

Figure 5 shows general views of the mandrel (6), consisting of a central rod (7) - a wedge of variable section and a set (8) of side rods along the perimeter of the wedge, in the general set corresponding in shape to the inner section of the bent waveguide and made by fit with a gap , to facilitate insertion and removal of the mandrel.

Figure 6 shows the cross section of the mandrel (6), where (7) the central rod is a wedge of variable cross section, and (8) the side rods along the perimeter of the wedge, in the general set corresponding in shape to the inner section of the bent waveguide.

The operation of the device consists of the following operations:

1) installing the mandrel into the waveguide by pulling the fastening element (3) from the side of the small section of the wedge, manually or using technological equipment (winch, lever, etc.);

2) bending in a pipe bender (with three rollers or with a rotating copier);

3) removal of the mandrel at the end of the bending operation by pulling in the opposite direction by the opposite fastening element manually or using technological equipment.

For a mandrel with a central pond, the difference in use lies in the fact that, to facilitate installation, the mandrel is tightened with a wedge (7) extended towards a larger section, then the set of bars (8) is compacted by tightening the wedge into the mandrel.

At the end of the waveguide bending operation, the wedge is extended, weakening the filling of the waveguide volume and reducing friction, which simplifies the removal of the mandrel from the waveguide.

Claims (1)

Mandrel for bending thin-walled waveguides of rectangular section, containing a set of flexible elements assembled in a package, made with the possibility of filling the internal cavity of the waveguide, characterized in that it is equipped with metal fastening elements located at both ends of the mandrel for installing and removing it from the waveguide, while the flexible elements are made in the form of rods, square in section, from a porous composite material, the structure of which includes materials with a lubricating effect.

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