RU2388601C2 - Method to produce negative curvature jackets - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to processing of plastic materials and can be used in architecture, construction and R&D works for testing strength properties. Proposed method consists in that the ends of the element of oriented or thermo-setting tubular thermo-softening plastic material have inserted rigid disks (for example, metal disks) with spreders are heated separately to high-elasticity state. Then the entire device is heated to high-elasticity state and heating is abruptly interrupted. In this process tubular thermo-softening plastic element is tightly clamped in disks to get negative curvature shape between disks, in particularly (in this case), the shape approximating to catenary surface. After removal from the frame, both catenary surface and its components separated mechanically into other jackets of negative curvature can be used.

EFFECT: efficient process of fabricating negative curvature jackets from thermoplastic materials, eg PVC, PMMA, PC-polycarbonate, PTFE etc.

3 cl, 2 dwg

Description

The invention relates to the field of plastics processing, namely the manufacture of shells of negative curvature from various thermoplastics (polyethylene, PVC-a, plexiglass-PMMA, PC-polycarbonate, PTFE-a, etc.).

It can be used in architecture and construction, as well as for research purposes in mechanical engineering.

For the formation of various forms of shells, an application was filed for an invention: “Shell structure and method of its manufacture” No. 2005140852/11 of 07/10/2007, in which the shell structure comprising a frame of interconnected longitudinal and transverse reinforcing elements, integral with gas-filled material, forming the shell of a given curvature, characterized in that the shell has an additional forming layer bonded to the frame.

The disadvantage of this method is the complexity of the steps of manufacturing the shell:

- the frame is assembled from longitudinal and transverse reinforcing elements;

- reinforcing elements are monolithically fastened with gas-filled material;

- the future shell is provided with an additional forming layer attached to the frame.

The disadvantage of this method is also the high material consumption:

- the presence of longitudinal and transverse reinforcing elements;

- monolithically fastening gas-filled material;

- additional forming equipment.

An application was filed for invention No. 94030083 of 08/11/1994 on the topic: "Formwork for the construction of shells of a curved shape and the method of its manufacture."

According to this application, bulk material, such as sand, is laid on the base, and the required curvature is set on the surface of the sand. Then the sand is moistened with liquid (water) and cold is passed into the sand through the heat exchanger. The liquid freezes, and the formwork surface becomes strong and solid, able to absorb the load from the concrete shell applied to it. Formwork is done by thawing water.

The disadvantages of this method are as follows:

- the surface of the sand cannot be given the required curvature - the sand will crumble, and if moistened, the surface will resemble the moon - with traces of meteorites;

- passing cold will slow down the hardening process of concrete; As is known, in concrete plants concrete hardens under the influence of hot steam.

There is an application for invention No. 93018659 "Formwork of adjustable curvature and a method for its manufacture" from 08.04.1993.

The invention relates to construction. To create a formwork with ease of manufacture and formwork, the formwork contains flexible elastic threads and formwork panels installed on them. A flexible shell is supported on the formwork panels, on which the concrete mixture is laid. Flexible elastic threads are fixed on supports. The formwork is brought into working position by tensioning flexible elastic threads on the supports

The disadvantages are as follows:

- the complexity of the formwork design: flexible threads with formwork panels installed on them; a flexible shell on top of the shields, and then only concrete mix is laid;

- the duration of the manufacturing process of the shell: fixing flexible threads with the ability to adjust their tension; laying shuttering boards; laying concrete mixture on a flexible shell (apparently, on soft rubberized).

There is a patent of the Russian Federation No. 22585864 dated 10.07.2005. "A method of manufacturing ribbed shells of negative curvature."

According to this method, two sheets of thermoplastic (oriented and ordinary) are clamped between the elements of the double frame (according to the invention, double arched elements) and are heated to a highly elastic state. As a result of the formwork, two shells are obtained: the upper one with a smooth surface, and the lower one with ribs.

The disadvantages of the invention are as follows:

- the frame is supposed to be double - for clamping both sheets of thermoplastic (conventional and heat-shrinkable), which increases the high cost of the method (extra frame element and clamping devices) and adds an extra technological step - the clamping process;

The prototype of this application is the invention according to copyright certificate No. 625231 of July 26, 1997, M.cl. G09B 23/00

"The method of modeling the surfaces of volumetric bodies."

The shell is made of heat-shrinkable plastic film, and after pressing it to the frame is heated to 100 ° C for 1-2 minutes, cooled and removed from the frame.

The simulation method is as follows:

- the workpiece is cut from a flat panel and clamped in a frame;

- after that, the film with the frame is heated to 100 ° C for 1-2 minutes.

When cooling, the softened film, trying to reduce its surface area, takes a curved shape. After removing the curved wall from the frame, the model is ready and m. easily reformed.

This method of manufacturing models (shells) has the following disadvantages:

- frame 2, for the manufacture of models 1 is integral, and integral (according to the drawing), therefore, the removal of finished models (shells) is problematic and sometimes impossible (based on the practical experience of the authors);

- the use for modeling only blanks from a flat panel of heat-shrinkable polyethylene film significantly limits the class of polymers, where in addition to PE there are other thermoplastics such as PVC, PMMA, polystyrene, polycarbonate, etc .;

- the impossibility of obtaining the tightness of the internal volume of the models, because models are made of flat panels;

- the need for clamping devices 3, which implies the high cost of this method and an extra process.

The invention is directed to the manufacture of shells of negative curvature.

The result is achieved in that in a method for manufacturing shells of negative curvature, including laying and securing a heat-shrinkable thermoplastic in a spatial frame and co-heating the frame with a thermoplastic, characterized in that the tubular element of the heat-shrinkable thermoplastic is first heated from one end to a highly elastic state and at the same time clamps the upper ring the frame, then heats up to a highly elastic state from the other end, clamping the lower ring in itself (although heating can be carried out by at both ends), and then with both rings clamped together by a collapsible core, the entire system is again heated to the beginning of a highly elastic state of the middle part of the future shell of negative curvature.

The method is characterized in that the frame is disassembled by unscrewing the rods from the collapsible core, and the finished shell remains with two rings (upper and lower). It also differs in that the shell of negative curvature with two clamped rings is subjected to internal pressure (pneumatic or hydro) for static mechanical tests.

A method of manufacturing shells of negative curvature is illustrated by drawings, where in Fig. 1 the numbers indicate: 1 - dotted line shrink tubular element in the initial state, the solid line is the molded shell, 2 - the right and left rings of hard material (for example, steel, aluminum or other ) with an internal thread, 3 - rods (right and left) with an external thread along the entire length of rigid material (steel, aluminum or others), 4 - a rigid metal collapsible core with an internal thread of steel or aluminum.

Figure 2 shows the finished shell of negative curvature, in this case, in the form of a catenoid.

As is known, a helicoid, as well as several other independent shells of negative curvature by cutting along, across, or along an arbitrary curve, can be obtained from a catenoid by mechanical influences (cutting along a generatrix).

A method of manufacturing shells of negative curvature from heat-shrink tubular elements is carried out in the following sequence:

- a space-rigid frame is assembled, consisting of two rings with an internal thread 2 and two rods with an external thread 3 connected through a collapsible core with an internal thread 4;

- on a spatially rigid frame consisting of elements 2, 3, 4, a heat-shrink tubular element 1 is put on, and the tubular element 1 is made with an inlet on both ends by an amount equal to 1/5 (approximately) the diameter of the rings 2;

- both ends of the system, consisting of elements 1, 2, 3, including internal parts, to a shallow depth (approximately 4-5 mm), are simultaneously or alternately heated until the heat-shrink tubular element 1 reaches a highly elastic state;

- when the heat-shrink tubular element 1 reaches a highly elastic state, the tubular element 1 at both ends begins to reduce its surface area, tightly and rigidly wraps around the right and left rings 2, while the heat-shrink properties are fully activated;

- then the middle part of the system consisting of elements 1, 2, 3, 4 is subjected to heating; the middle part of the heat-shrink tubular element 1, reaching a highly elastic state, reducing its surface area, perceives the shape of the shell of negative curvature, in particular the shape of the catenoid or close to it;

- in this process, the spent ends (right and left) of the tubular heat-shrinkable element 1, which sealed tightly and rigidly the right and left rings 2, serve as clamps when negative curvature is formed in the middle part of the shell.

Technical appraisal and economic advantages of the invention are as follows:

- there is no need for any clamping devices for attaching the heat-shrink tubular element to the frame;

- the finished shell is easily removed from the frame by unscrewing the rods from the core and trimming the spent ends of the tubular element 1;

- it creates the possibility of obtaining a shell of negative curvature with an internal sealed space in the case of plugging in both rings of threaded holes;

- in the case of plugging a threaded hole in only one ring and installing an inlet nipple in another ring to supply air or water, it becomes possible to test the sheath for mechanical strength.

Claims (3)

1. A method of manufacturing shells of negative curvature, including laying and fixing a heat-shrinkable thermoplastic in a spatial frame and co-heating the frame with thermoplastic, characterized in that the tubular element of the heat-shrinkable thermoplastic is first heated from one end to a highly elastic state and at the same time clamps the upper ring of the frame, then heats up to a highly elastic state from the other end, clamping the lower ring in itself, and then with both rings clamped together by a collapsible core m, the entire system is reheated prior to highly elastic state the middle part of the future shell of negative curvature. 2. The method according to claim 1, characterized in that the frame is disassembled by unscrewing the threaded rods from the core and the rings of the upper and lower, and the finished shell remains with two rings of the upper and lower. 3. The method according to claim 1, characterized in that the shell of negative curvature with two clamped rings is subjected to internal pressure pneumatic or hydro for static mechanical tests.

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