RU2469849C1 - Knock-down mandrel for making shells from composite materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: mandrel comprises central shaft, set of lengthwise forming elements arranged thereabout, and end fasteners. Said forming elements are shaped to one-diameter curvilinear tubes arranged in circle of diameter D_cir-D - d where D and d are diameters of mandrel and tubes, respectively. Note here that radii of tube curvature represent set of values in the range of

where R_ax is radius of mandrel curvilinear axis. Note also that grooves between said tubes are filled with flexible sections with face surfaces making mandrel working surface.

EFFECT: ease of withdrawing mandrel elements from finished products.

3 cl, 5 dwg, 6 ex, 5 tbl

Description

The invention relates to technological equipment for molding products from composite materials based on strong fibers and a polymeric binder, and can be used when winding curved shells, for example pipe bends.

Known mandrel for winding pipes made of composite materials containing a split shell with longitudinal edges, a Central shaft fastened by ribs with a shell, and a device for changing the diameter of the shell, made wedge-shaped and located between adjacent edges of the longitudinal edges of the shell (RF patent No. 2290310 from 12.27.2006) .

The use of a well-known technical solution in relation to the mandrel for forming curved shells will be associated with great technological difficulties in the manufacture of components and parts of the mandrel, as well as when removing the manufactured shell from the mandrel.

Known collapsible mandrel for the manufacture of high-strength shells of composite materials, containing a Central shaft, a set of longitudinal forming elements located around it, end fasteners (RF patent No. 2147003 from 03/27/2000). The mandrel is intended for winding shells of complex shape with a straight axis. This mandrel is adopted as a prototype.

Signs of the prototype, coinciding with the signs of the claimed invention, the Central shaft; a set of longitudinal forming elements located around it; end fittings.

The reasons that impede the achievement of the technical result indicated below when using the known device adopted for the prototype include the fact that the known device is laborious to manufacture and will require significant financial costs. This is due to the complex geometry of the forming elements, which will be the longitudinal segments of the torus, with the double curvature of the front surface forming the working surface of the mandrel, and with developed side edges. Obviously, the metal consumption and the complexity of obtaining blanks for segments will be significant, and finishing machining is difficult and costly. This will be especially characteristic for mandrels of large diameters (300 ... 800 mm). The forming elements for them will be large and heavy, which will complicate their removal from the finished product.

The task to which the invention is directed is to simplify the design of the mandrel, reduce the complexity and costs of its manufacture, facilitate the removal of its elements from the finished product.

, где R_ос - радиус криволинейной оси оправки, а канавки между криволинейными трубками заполнены гибкими профилями, лицевая поверхность которых образует рабочую поверхность оправки. В качестве радиусов кривизны трубок взяты радиусы их вогнутых образующих. Гибкие профили изготовлены из упругоэластичного материала, например теплостойкой вулканизованной твердой резины.The problem is solved due to the fact that in the known device containing a central shaft, a set of longitudinal forming elements located around it, end fasteners, forming elements are made in the form of curved tubes of the same diameter, arranged around a circle with a diameter D _okr = Dd, where D and d are the diameters of the mandrel and curved tubes, respectively, while the radii of curvature of the tubes are a combination of values in the range

where R _OS - the radius of the curved axis of the mandrel, and the grooves between the curved tubes are filled with flexible profiles, the front surface of which forms the working surface of the mandrel. The radii of curvature of the tubes are taken as the radii of curvature of the tubes. Flexible profiles are made of an elastic material, such as heat-resistant vulcanized hard rubber.

, где R_ос - радиус криволинейной оси оправки; канавки между криволинейными трубками заполнены гибкими профилями, лицевая поверхность которых образует рабочую поверхность оправки; в качестве радиусов кривизны трубок взяты радиусы их вогнутых образующих; гибкие профили изготовлены из упругоэластичного материала, например теплостойкой вулканизованной твердой резины.The features of the proposed device, distinctive from the prototype, - the forming elements are made in the form of curved tubes of the same diameter, located around a circle with a diameter of D _okr = Dd, where D and d are the diameters of the mandrel and curved tubes, respectively; the radii of curvature of the tubes are a set of values in the range

where R _OS - the radius of the curved axis of the mandrel; the grooves between the curved tubes are filled with flexible profiles, the front surface of which forms the working surface of the mandrel; the radii of curvature of the tubes are taken as the radii of curvature of the tubes; flexible profiles are made of an elastic material, for example heat-resistant vulcanized hard rubber.

Consider the distinguishing features in more detail, comparing the prototype with the proposed solution:

- in the prototype, the forming elements are made in the form of complex thick-walled longitudinal segments, the complexity and metal consumption is significant, especially with large diameters of the mandrel (300 ... 800 mm). In the proposed solution, the forming elements are curved tubes of the same diameter, these tubes are thin-walled, lightweight, they are small in diameter (20 ... 50 mm). Tubes of the desired diameter are available and inexpensive to purchase, the bending technology is simple, the manufacturing effort is small;

- in the prototype, the forming elements are joined together by inclined lateral faces; in order to exclude ledges at the joints, it is necessary to ensure the accuracy of the manufacture of elements and their fitting in place. In the proposed solution, lateral docking of the tubes is not required; here, gaps between the sides of adjacent tubes are allowed;

- in the prototype, the working surface of the mandrel is formed by the external profiled sides of the segment elements. In the proposed solution, the working surface is formed by the front surface of the flexible profiles of the elastic material. Flexible profiles are easy to manufacture, they can be obtained by extrusion through a profile die or by laying out rubber blanks in place on the mandrel, with shaping and subsequent vulcanization;

- in the prototype, the forming elements with large diameters of the mandrels (300 ... 800 mm) have significant dimensions and weight, which complicates the assembly of the mandrel, and especially the disassembly and removal of its elements from the finished product. In the proposed solution, the forming elements are curved thin-walled light tubes. They are convenient when assembling and disassembling the mandrel. Flexible profiles by weight and size also do not cause difficulties when assembling and disassembling the mandrel.

Thanks to these distinctive features, the design of the mandrel is simplified, the complexity and costs of its manufacture are reduced, and the extraction of its elements from the finished product is facilitated.

The proposed technical solution is illustrated by the drawings shown in figures 1-5. Figure 1 shows a General view of the mandrel, figure 2 is a cross section of the mandrel; figure 3, a is a longitudinal forming element is a curved tube; figure 3, b is a flexible profile; figure 4 shows a diagram for determining the radii of curvature of the tubes of the experimental mandrel; figure 5 is a fragment of the manufacture of an experimental mandrel.

The mandrel has a central shaft 1, a curved axis 2 of a given radius R _OS . Around the Central shaft 1 are located around a circle with a diameter of D _okr longitudinal forming elements 3 made in the form of curved tubes of the same diameter d with the radii of curvature of the concave generatrix R _i . Tubes 3 are installed at their ends and secured to end parts 4. The grooves between the tubes 3 are filled with flexible profiles 5, their front surface 6 forms the working surface 7 of the mandrel. All curved tubes 3, flexible profiles 5, as well as their locations in the mandrel are marked 8.

The assembly of the mandrel consists in the sequential installation and fastening of the curved tubes 3 on the end parts 4, previously fixed on the Central shaft 1. This is done in accordance with the marking. After that, flexible profiles 5 are laid in the grooves between the tubes 3 and fixed with fasteners 4. Do this also in accordance with the marking.

The mandrel is used in the work as follows.

It is fed to the winding machine and is fastened to the ends of the central shaft 1 by clamping devices. Then, a fluoroplastic tape is wound on the working surface 7 of the mandrel, forming a release layer. Then they go directly to the formation of the product, for example fiberglass elbow, using the spiral-ring method of winding. After winding, casing of the casing in the heating cabinet and subsequent removal of the mandrel follow.

Dismantling and removal of the mandrel elements from the finished product is carried out in the following order. The ends of the tubes 3 and flexible profiles 5 are detached from the end parts of the fastening 4, which are then removed from the ends of the central shaft 1. The central shaft 1 thus freed is freely removed from the inner cavity of the mandrel. Then, the detached curved tubes 3 and flexible profiles 5 are subsequently removed, shifting them first in the radial direction to the axis 2 of the mandrel, and then in the longitudinal direction. Due to the dividing fluoroplastic layer, the lightness of the tubes 3 and profiles 5, as well as their small cross-section, the process of removing the mandrel elements is quite facilitated.

An example of the execution and testing of the mandrel

Initial data: mandrel with a diameter of D = 126 mm for a branch with a rotation angle φ = 90 °, the radius of curvature for the mandrel R _oc = 2D = 2 · 126 = 252 mm.

We take as a blank for forming elements a steel smooth thin-walled tube with an outer diameter of d = 22 mm and a wall thickness of δ = 1 mm. It is inexpensive and affordable.

Determine the number of formative elements. The diameter D _okr , on which we place the tubes, is equal to D _okr = Dd = 126-22 = 104 mm. The length of this circle will be L = π · D _okr = 3.14 · 104 = 326 mm. We set the gap between the tubes with their uniform arrangement, we take Δ = 5 mm. Determine the estimated number of tubes

We accept the number of tubes n = 12 pieces.

We determine the layout of the tubes, the most rational is shown in Fig.4. Here the tubes are located symmetrically relative to the coordinate axes X, Y, which provides a smaller number of tube sizes; in this embodiment, there are 6 mandrels, two tubes of each size.

Next, we determine the radii of curvature R _{i of} each pair of tubes. There are two ways to do this: graphical and analytical, using trigonometric functions. Let's take a simpler graphical way. We perform a geometric drawing of the cross section of the mandrel in a scale of 1: 1, with the given values of the parameters of the designed mandrel D, d, D _okr , R _OS , n (Fig. 4). From this drawing, we measure the distance from the vertical axis Y to the concave generatrix of each tube located above the X axis. So for tube No. 1, this is segment b ₁ = 25 mm, for tube No. 10 we measure segment b ₁₀ = 38 mm. For other tubes, measurements are similar. The radii of curvature of the tubes are calculated by the formulas:

for tubes to the right of the axis YR _i = R _oc -b _i

for tubes to the left of the axis YR _i = R _oc + b _i

The calculation results are summarized in table 1.

Table 1 The radii of curvature R _i tubes No. of curved tubes 3.4 2.5 1,6 7.12 8.11 9.10 Radii of curved tubes, R _i , mm 192 205 227 255 277 290

Note that this method of determining R _i gives an error of ± 1%, in comparison with the second analytical calculation using trigonometric functions.

Next, we calculate the length of the workpiece for each tube. We use the formula

The calculation results are summarized in table 2.

table 2 Length of tube blanks Tube number 3.4 2.5 1,6 7.12 8.11 9.10 The length of the workpieces, ℓ _i , mm 301 322 356 400 435 455

The total length of the tubes is L = 4538 mm. According to the values of R _{i of} table 1, cardboard templates were made. According to these templates, 6 pairs of tubes were bent on the bending device and immediately marked in accordance with FIG. 4. Then, according to the marking, they were installed on the end parts. This fragment is shown in figure 5.

A flexible profile with a length of about 5 m was obtained by extrusion of crude rubber grades 51-1615 through a profile die with the appropriate geometry. Then, the profile was cut into segments and marked according to table 2. Next, according to the marking, these profiles were placed in the grooves between the tubes, they were milled in place on the mandrel and vulcanized in a heating cabinet.

On the assembled mandrel, trial winding and curing of the fiberglass billet was carried out. As expected, the dismantling of the mandrel and the removal of its elements from the product took place without difficulty and quickly, in 7 minutes.

1. Examples of determining the claimed range of values of R _i

Example 1

Manufactured and tested mandrel has the following parameters:

D = 126 mm; R _OS = 2D = 252 mm; d = 22 mm; Δ = 5 mm; _Env D = 104 mm.

We define for this mandrel the range of values of R _i , substituting the values of its parameters in the expression

After calculations, we obtain the interval

Table 1 shows the values of R _i for this mandrel: 192; 205; 227; 255; 277; 290 mm.

Note that all the values of R _i fit into the interval (2); There are no values that fall outside the range. If transcendental values of R _i had occurred, tubes with these values of the radii of curvature would not fit into the cross section and the volume of the mandrel. Let us explain the foregoing by example, using table 1 and figure 2.

Take two tubes: No. 3 and No. 10. For tube No. 3 R ₃ = 192 mm, for tube No. 10 R ₁₀ = 290 mm. Change these values to the beyond: take R ₃ = 180 mm and R ₁₀ = 300 mm. With such curvature, these tubes do not fit into a given cross-section of the mandrel, they go beyond the circle D = 126 mm. As a result, we get a mandrel with an oval cross section, which is unacceptable for the manufacture of a branch, since the section at the branch must be round.

Thus, if we choose the values of the radii of curvature of the tubes for a given mandrel outside the interval (2), then we will not get a round cross-sectional shape, which is unacceptable to a mandrel for taps.

Example 2

Mandrel with parameters: D = 240 mm; R _OS = 480 mm; d = 30 mm.

Define for this mandrel the range of values of R _i

After calculations, we obtain the interval

Example 3

Mandrel with parameters: D = 500 mm; R _OS = 1000 mm; d = 50 mm.

Define a mandrel for this range of values R _i

After calculations, we obtain the interval

From the considered examples, the conclusions follow:

- each mandrel size has its own interval of values of the radii of curvature of the tubes;

- the specific value of the radius of curvature for each tube of this mandrel is determined by the methodology described in the description of the invention; all these values fit into the interval R _{i of the} given mandrel;

- with an increase in the diameters of the mandrels, the range of values of R _i expands;

- the choice of values of the radii of curvature outside the interval (2) is unacceptable, it does not provide a round cross-section to the mandrel.

2. Determining the area of effective application of the solution of the claimed technical solution.

In view of the foregoing, we believe that it is advisable to indicate the limits of the declared interval using the allowable limits of variation of the parameters included in expression (1). Define the boundaries of the parameters D, R _OS , d, providing the claimed technical result.

a) The parameter d is the diameter of the curved tubes.

Obviously, the diameter of the tubes should be chosen based on the mandrel, its diameter. The larger the diameter of the mandrel, the greater the number of tubes in the mandrel. The curvature of the tubes is ensured by bending straight workpieces. Steel thin-walled tubes with a diameter d of not more than 50 mm are bent sufficiently, accurately and simply. Their bending is carried out on a simple bending device. Tubes with a diameter in the range of 50 mm <d≤100 mm are pre-filled with sand, heated, and then bent to the desired radius in the installation. The bending of tubes with such diameters is laborious, the accuracy of the radius is reduced compared to tubes d≤50 mm Even more time-consuming and expensive technology for bending large-diameter pipes. They are also filled with sand, heated and then bent in special powerful bending machines.

Given the above, we accept the interval of values of the diameters of the tubes

Such tubes contribute to the achievement of the claimed technical result.

b) The parameter R _OS - the radius of the curved axis of the mandrel.

In the practice of designing mandrels for the manufacture of fiberglass bends, it is customary to set R _OS depending on the diameter of the mandrel, within the following range:

Mandrels with such a curvature of the axis make it possible to obtain high-quality winding of the tap, which means that they will achieve the claimed technical result.

c) The parameter D is the diameter of the mandrel.

Consider the main parameter included in expression (1). Define the lower limit of the values of D, providing the claimed technical result.

Mandrels of small diameter (D≈30 ... 100 mm) are often made of sand-polymer, pouring into a technological form, followed by curing. They are simple in design and available to manufacture. The use of such mandrels with D> 100 mm is limited, since the manufacture of the technological form is complicated, the consumption of materials increases, and they are also disposable.

In view of the above, for the lower limit of the claimed range of values of D, we take D = 100 mm. The experience of manufacturing and testing a mandrel of approximately this diameter (D = 126 mm) confirmed the claimed technical result.

The upper limit of the values of D is determined by three examples. First, we note that the larger the diameter of the mandrel, the greater the number of curved tubes should be part of it, the larger the diameter should be taken tubes. This is obvious and follows from the principle of rationality.

Example 4

Mandrel with parameters: D = 800 mm; R _OS = 2D = 1600 mm; d = 50 mm; D _okr = Dd = 750 mm; the gap between the tubes Δ = 20 mm

Determine the number of tubes

The same number of flexible profiles will be required (see FIGS. 2, 3). The number of fasteners for the tubes will be 2n = 2 × 34 = 68 sets. The dimensions of such a mandrel will be about 2 × 2 m.

The manufacture of a mandrel of such a large diameter, with a large number of different elements, large dimensions, is significantly labor intensive. The assembly and disassembly of such a mandrel is complicated and will require considerable time. It should be noted that companies engaged in the production of fiberglass pipelines usually do not use mandrels for taps of large diameters, but do a tap of 3; 4 rectilinear fiberglass sections with oblique sections of the mating ends, which are assembled into a single structure, gluing the ends and reinforcing the joints by winding glass material with a binder.

From the foregoing it follows that for a mandrel with a diameter of D = 800 mm it is inappropriate to use the claimed design solution; here it is hardly possible to get the claimed technical result.

Example 5

Mandrel with parameters: D = 650 mm; R _a = 1300 mm; d = 50 mm; Δ = 20 mm; D _okr = 600 mm.

The number of curved tubes will be

округляем до четного n=28.

round to even n = 28.

The same number of flexible profiles will be required, the number of fasteners will be 2n = 56 sets. The assessment of the appropriateness of such a mandrel is similar to example 4.

Example 6

Mandrel with parameters: D = 500 mm; R _OS = 1000 mm; D _okr = 450 mm; d = 50 mm; Δ = 20 mm.

The number of curved tubes is equal to

The same number will be flexible profiles, the number of fasteners is 2n = 40 sets.

Let us analyze this size mandrel. In comparison with examples 4; 5 the number of curved tubes, flexible profiles, fasteners in this embodiment is significantly less; the dimensions and weight of the tubes, flexible profiles and mandrels are also smaller.

Considering the positive experience in the design, manufacture and testing of a mandrel with D = 126 mm, with its complexity of manufacturing, the number of elements, the time for its assembly and disassembly, the convenience of removing the mandrel parts from the product, transforming all this into a mandrel with a diameter of D = 500 mm, we conclude that it is implementing the claimed technical result.

We take the value D = 500 mm as the upper limit of variation of the main parameter of the mandrel - its diameter. As a result, we take the following range of mandrel diameters for which the claimed technical result is realized

For mandrels with D values that fall outside this interval, the application of the proposed technical solution will not provide the possibility of obtaining the claimed technical result.

Thus, the permissible ranges of the values of the parameters of the mandrel are defined:

The indicated intervals of the parameters of the mandrels in their totality will provide the opportunity to obtain the claimed result: simplification of the mandrel design, reducing the complexity and costs of its manufacture, ensuring dismantling and removal of the mandrel parts from the product.

Claims (3)

1. The mandrel is collapsible for the manufacture of shells from composite materials, containing a central shaft, a set of longitudinal forming elements located around it, end fasteners, characterized in that the forming elements are made in the form of curved tubes of the same diameter, arranged around a circle with a diameter of D _okr = Dd , where D and d are the diameters of the mandrel and curvilinear tubes, respectively, while the radii of curvature of the tubes are a set of values in the range

,
where R _OS - the radius of the curved axis of the mandrel, and the grooves between the curved tubes are filled with flexible profiles, the front surface of which forms the working surface of the mandrel. 2. The mandrel according to claim 1, characterized in that the radii of their concave generators are taken as the radii of curvature of the tubes. 3. The mandrel according to claim 1, characterized in that the flexible profiles are made of an elastic material, for example heat-resistant vulcanized hard rubber.

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