DE1126125B - Method and arrangement for the production of bellows from plastic that is deformable in the heat - Google Patents

Description

The invention relates to a method for manufacturing bellows. In the production of Bellows made of fabrics that are stretchable, such as some metals, or thermoplastic, such as rubber, gutta-percha or balata or other polymeric materials, a variety of methods can be used. These include the Shaping by hot or cold means under pressure or during a flow molding process which the material takes on the desired shape.

The subject of the invention is a method for the manufacture of bellows made of heat-deformable bellows Materials, namely fluorine-containing materials that have only limited thermoplasticity and as a result are difficult to deform, but on the other hand have properties, which make them particularly suitable for the required purpose.

According to the invention there is the method for the production of bellows, wherein ring-shaped cut Sheets of plastic placed one on top of the other and along their edges using Pressure and heat are combined in pairs, in that the leaves are made from one block of one Fluorine-containing polymer cut and to achieve the inner edge connection parallel to its plane of the sheet except for a collar from the outside which results in the inner edge connection are welded forth or that each two annular sheets lying one on top of the other on their inner Scope to be connected to each other.

Then a heat-resistant sheet is placed between the sheets that are not to be connected, along their outer edge Frame inserted, followed by joining the outer edges of the leaves with simultaneous action of pressure and heat is brought about in a manner known per se by a sintering process.

A number of similarly shaped parts are connected at the edges. This The process includes fastening by means of adhesives or, where appropriate, by means of soldering, brazing or welding one.

The individual parts can be circular, triangular, rectangular, trapezoidal or polygonal according to the shape required for the finished bellows.

The frame for insertion between the sheet edges that are not to be connected is preferably made of metal produced, and an arrangement has been found to be suitable for implementation, which consists of a Bracing device consists, which has a threaded rod, one at each end

for the production of bellows

Made of plastic that can be deformed under heat

Applicant: Dunlop Rubber Company Limited, London

Representative: Dipl.-Ing. E. Rathmann, patent attorney, Frankfurt / M., Neue Mainzer Str. 40-42

Claimed priority: Great Britain September 15, 1956 (No. 28 274)

Charles Derrick Dunkley, Manchester, Lancashire,

and Bryan Vivian Guy Martin,

Wilmslow, Cheshire (UK) have been named as inventors

Metal plate is provided, the diameter of which is greater than the outer diameter of the frame is sized.

Bellows made of polytetrafluoroethylene or polytrifluorochloroethylene are used as expansion seals in pipelines that contain corrosive liquids, such as. B. acids and alkalis, because these polymers have remarkable chemical resistance and are not attacked by either chemicals or solvents. Such bellows remain over a large temperature range, for example between -70 and +250 ⁰ C, functional. They have good electrical insulation properties and their absorption capacity for water is zero at all temperatures. They also show exceptional flame-retardant properties.

In the manufacture of such bellows, a number of similarly shaped sections are made of polytetrafluoroethylene or polytrifluorochloroethylene placed on top of one another, with appropriately shaped spacers made of metal or another non-adhesive and heat-resistant material at the edges interposed in this way that they lie on the sides facing away from the sides to be glued, one after the other, according to the in the desired number of turns on the bellows. This arrangement is clamped and by means of a

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or several clamping plates subjected to a compression. The whole thing is then, e.g. B. in an oven, heated to a sufficiently high temperature and exposed to this temperature for a long enough time to allow the plastic parts to where they are under pressure through the intermediate pieces to be welded together.

If a number of individual platelets are used, the inner and outer plates can be used Edges are joined together either at the same time or in separate operations. Have on the other hand, the preformed parts take the form of pocket-like envelopes and are therefore already connected to one another at one of their edges, a single welding process is sufficient.

If desired, a fluorocarbon based welding paste can be used or a layer of unsintered polytetrafluoroethylene is applied to the edges of the preformed sections to support the welding process.

Such a welding paste contains e.g. B. 35 parts by weight of polytetrafluoroethylene press powder mixed with 65 parts by weight of a liquid fluorocarbon. When used, a thin spread is applied brought one surface and placed the second surface on top and pressed. By heating to around 360 ° C, the two surfaces become one another tied together.

The unsintered strip is prepared by mixing about 80 parts of large particle size polytetrafluoroethylene powder with 20 parts by weight of a lubricant such as e.g. B. a mixture of turpentine oil substitute or a solution of about 1% polyisobutylene in petroleum naphtha. This mixture is squirted into a strip, from which the lubricant will evaporate when heated ^{to around 360 3 C.}

Various types of terminations can be attached to the bellows, either during the initial welding process or afterwards through localized heating.

The method of making bellows according to the present invention will now be described with reference to FIG Examples explained with reference to the drawings.

Fig. 1 shows schematically a pocket-shaped Polytetrafluoroethylene disc;

2 shows schematically a pocket-shaped disk with an inserted metal intermediate piece;

FIG. 3 shows several panes according to FIG. 2 placed one on top of the other before they are welded to form bellows.

example 1

First, a cylindrical block of polytetrafluoroethylene with an outside diameter of 10.16 cm and a length of 6.35 cm and a central hole of 2.22 cm diameter is produced by sintering in a known manner. These dimensions βο are suitable for the production of a circular bellows with an outside diameter of 10.16 cm and a center hole of 2.54 cm diameter.

Thin slices 10.16 cm in diameter, with a central hole, are made from this block 2.54 cm in diameter and 0.081 cm thick. During the separation process If the discs are split up to 0.48 cm from the center hole, so one To obtain pocket-shaped disc, which is shown in Fig. 1 of the drawings.

Metal rings 1 (split if desired) shown in Figure 2 with an outside diameter of 10.16 cm are on the outer edges of each split disk between the opposing ones Placed surfaces. A number of disks are, as shown in Fig. 3, placed one on top of the other, so that the outer edges of the discs are in contact with each other to obtain the required number of turns.

This arrangement is then braced by means of a threaded rod, the The rod carries metal plates with a larger diameter than that of the rings at both ends, as well as by means of nuts that can be tightened so that the metal plates on the outer edges of the Slices exert a pressure. The whole is placed in an oven at one temperature for 90 minutes set at 360 ° C to weld the edges together, and then taken out and refrigerated. The jig and the metal rings will be away from the bellows.

Example 2

From a cylindrical block made of polytetrafluoroethylene 7.62 cm in diameter, which has a cylindrical hole 3.18 cm in diameter cut a series of 0.025 cm thick slices. These discs come along with circular metallic spacers between the inner edges of two discs each and similar pieces placed one on top of the other between the outer edges, with the inner and outer Intermediate pieces are always offset by half a step so that the inner intermediate pieces are the sides of the disks opposite to those touched by the outer ones. This arrangement will clamped as in the previous example and heated for 90 minutes at 360 ° C until the inner and outer The edges of the panes are alternately welded. After cooling, the jig and removed the intermediate rings from the bellows. It can produce bellows of any length are according to the number of discs used.

Claims (3)

PATENT CLAIMS: 1. A method of manufacturing bellows from thermally deformable plastic, wherein sheets cut into a ring from that plastic are placed on top of one another and joined in pairs along their edges with the application of pressure and heat, characterized in that the sheets are cut from a block of a fluorine-containing polymer and to achieve the inner edge connection parallel to its sheet plane up to a collar which results in the inner edge connection, or that two annular sheets lying one above the other are connected to one another on their inner circumference and that then between the sheets that are not to be connected, along their outer edge, a heat-resistant frame is inserted, whereupon the connection of the Outer edges of the leaves under the simultaneous application of pressure and heat is brought about in a manner known per se by a sintering process. 2. Framework for carrying out the method according to claim 1, characterized in that this is made of metal. 3. Arrangement for carrying out the sintering according to the method according to claim 1, characterized in that that a bracing device from a threaded rod is used, at each end of which a metal plate is provided is whose diameter is dimensioned larger than the diameter of the frame. Documents considered: German Patent No. 900 268; French patent specification No. 880 584. 1 sheet of drawings