IE41825B1 - Pipe bend - Google Patents

Abstract

1491041 Sheet forming HOECHST AG 21 Oct 1974 [24 Oct 1973] 45382/74 Heading B5A [Also in Division F2] A one-piece plastics pipe-bend 101 in the shape of a portion of a hollow ring is open or overlapping along its innermost arc, the pipe bend 101 having been formed by bending from an inherently dimensionally stable shell-type body 10 having no re-entrant curves, the pipe bend 101 also being inherently dimensionally stable in its bend conformation. Thus through the forms 10, 101 may be interconverted, neither form tends to change shape by itself. The shell-type body 10 is made from plastics film by deepdrawing or by blow moulding, the latter yielding a flask-like structure composed of two bodies 10 joined along edges 28. Sufficient stability is conferred upon the body in the bend state 101 by thermal treatment of the material in that conformation. Alternatively, a complete torus may be manufactured and then divided into segments 101, which are opened out and heattreated in the shell-type form 10. To increase stability in the bend state 101, a corrugation 14 may be provided to extend along the outermost arc of the ring in the bend conformation 101, or the body 10 may be formed in such a shape that its corresponding bend state 101 has at least the mid-portions of its outermost and innermost arcs on different centres of curvature, preferably such that the radial distance between the arcs is less at the mid-portion of the bend than at the ends. Extended areas 12 of the body 10 provide for overlap along the innermost arc of the bend 101 where engaging means such as complementary notches or press studs may be utilized.

Description

This invention relates to pipe bends (or articles for covering elbows in pipes), and to processes for their manufacture. In British Patent Specification No. 1,150,094 a process for the manufacture Of shaped pipe bend components is disclosed in which a sheet of plastics film is formed, by deep-drawing, into the shape assumed by a pipe bend of up to 180° of arc, preferably a quarter segment which is cut along its smallest internal circular arc, and then drawn out until a shell having no re-entrant curves is produced, overlapping edges being added to the cut edges.

Such one-piece pipe bends are simpler and cheaper in their manufacture than other known pipe bends consisting of two deep-drawn half shells welded together at their outer meeting edges. Because of the manner of their manufacture, however, the above one-piece bends are not inherently stable in the configuration which they must assume after installation, because they have a tendency to return to the shell-type configuration in which they were formed. This tendency complicates their installation and may damage their outward appearance if the installation is not carefully performed.

The present invention is concerned with a onepiece pipe bend for sheathing thermal or sound proofing insulations, which pipe bend can be assembled more easily than previously proposed one-piece pipe bends and is acceptable in appearance after installation, even if no oarticular skill is employed in its installation. 'l'he invention accordingly provides a one-piece plastics pipe bend comprising a sheet, preferably a thermoformed sheet, in the shape of a portion, preferably a quarter, of a hollow ring, the pipe bend preferably being of circular section, which is open along its innermost arc, said pipe bend having been formed, by bending, from an inherently stable shell-type body having no re-entrant curves, the pipe bend also being inherently stable in its portion of a hollow ring conformation.

In the present specification, the term inherently stable as applied to the shell-type body having no reentrant curves means that the body has no tendency to change its form by itself, but may be converted, by the influence of external bending forces, into an inherently stable pipe bend corresponding for example to a quarter torus (90° sector) cut open along its innermost circular arc.

With reference to the pipe bend when in the form of a quarter torus (90° sector) open along its innermost circular arc, the expression Inherently stable means that the torus sector is not inclined to change its form by itself, but may be converted, by the influence of external bending forces, into an inherently stable shelltype body having no re-entrant curves.

In the present specification, the term shelltype body having no re-entrant curves means a body whose shape is such as would be produced by opening out the cut edges of a pipe bend of the form of a sector, especially a quarter of a torus (90° sector) cut along its innermost circular arc and bending the edges back.

A quarter torus (90° sector)1' is a sector of a generally circular cross-section pipe the two ends of which extend in planes which are at right angles to each other.

The present invention also provides a plastics body that is inherently stable in each of two forms, one form being shaped for covering an elbow in a pipe, and comprising a portion of a hollow ring open along an inner arc, the other form being an open and open-ended trough, herein also referred to as a shell-type body, having no re-entrant curves, the depth of the central portion of the trough being greater than that of the ends.

The invention further provides a process for the manufacture of a body inherently stable both in the form of an open and open-ended trough having no re-entrant curves, of which the central portion is deeper than the ends and also in the form of a portion of a hollow ring open along an inner arc, in which form it may be used for covering an elbow in a pipe, which comprises forming a plastics sheet into an inherently stable trough form, bending it into the ring form, and heat-treating the body while maintaining it in the ring form to render it inherently stable in that form without depriving it of its inherent stability in the trough form; preferably the trough form is manufactured by deep-drawing.

The pipe bend according to the present invention does not spring back by itself when it is placed in its torus sector state around an insulated pipe bend or the like. Therefore it can be easily fitted by a single person, even with limited space, and has a good appearance when installed. By bending, however, the pipe bend according to the invention may be converted into an inherently stable, shell-type body having no re-entrant curves.

Several embodiments of the invention will be described by way of example only, with reference to the accompanying drawings, in which:Fig. la shows a shell-type body consisting of and formed from a sheet of plastics film, which body Is such as would be produced by cutting a shaped body of resilient plastics film in the form of a 90° sector of a torus along its smallest meridional circular arc, bending the cut edges back until a body or shell having no re-entrant curves results, and adding an overlapping area to at least one of the cut edges. 4182S The three-dimensional structure of the shell-type body is described in the above mentioned Patent Specification. The body or shell described therein, however, is inherently stable in this shape only, and tends to return to this shape even after it has been bent into the torus sector shape it is to assume after installation, as a sheathing of a pipe bend. This tendency impedes the installation of the known shells. The shell according to Fig. la, however, may be converted into an inherently stable pipe bend by bending, as shown in phantom in Fig. lb.

Fig. lc shows a stack of shells, Fig. blowmolding, Id shows a pair of shells as formed by and Fig. le shows a continuous deep drawing series of shells as formed by a process.

Figs. 2a and 2b are perspective views of one embodiment of the pipe bend according to the invention, before and after installation.

Figs. 3a and 3b are diagrammatic meridional sectional views of two embodiments of the invention, Figs. 4 and 5 show examples of latch members which may be provided at the meeting edges to be joined together of the pipe bend according to the invention,. and Figs. 6 to 9 are sectional and perspective views of other latch members.

Referring now to the drawings, the pipe bend 10' formed, by bending, from the shell-type body or shell 10 shown in Fig. la is of such a structure that it is also inherently stable in the state of the closed or almost closed torus sector shown in Fig. 2a, for example. Overlapping areas are designated by the numeral 12. Thus, if a deformed sheet of plastics film 10 according to Fig. la is bent to form a torus sector-like structure 10', (indicated by the dotted line in Fig. lb) this structure retains its shape at least substantially and does not have the tendency to return by itself to the completely opened-out shell-like structure 10 having no re-entrant curves shown in Fig. la.

The inherently stable pipe bend 10' of the invention may be converted into an inherently stable shell-type body 10, by opening out the meridional cut edges 24 of the pipe bend 10' and inverting it in such a manner that a shell-type structure 10 having no reentrant curves results? by bending and inverting the shelltype structure in the opposite direction, the inherently stable shell may be re-converted into the inherently stable pipe bend. Thus, the - conversion from one inherently stable state into the other inherently stable state is reversible.

The one-piece pipe bends or sheathings 10' according to the invention may be stacked in the form of shells 10 as shown in Fig. lc so that a large number of shells IO may be fitted into one another. The installation of these shells 10 is very easy, because the shells converted into the shape of a pipe bend by a bending operation are inherently stable in this shape, too.

According to the present invention, a sheet of plastics film 10 of the kind shown in Fig. la is deformed in such a manner that it is also inherently stable in the form of a closed or nearly closed torus sector, as shown, for example, in Fig. 2b. If a deformed sheet of plastics film 10 according to the invention is bent into a torus sector-like structure 10', it retains this form at least substantially and shows no tendency to return to the openedout shell-type body 10 having no re-entrant curves.

The stability in the torus sector state may be produced by different means, which may be used either individually or in combination with each other.

The first of these measures consists in that the shell-type sheet of plastics film 10 produced by deepdrawing is forced to assume the torus sector shape 10' and is subjected to a heat treatment in this state, so that the tensions created by the bending operation are reduced at least to such a degree that the states of the closed or nearly closed torus sector as shown, for example, in Figs. 2a and b, are also inherently stable.

The tendency of the deformed sheet of plastics film 10 to retain the torus sector state 10' given to it during deformation may be increased by a meridional corrugation 14 which preferably extends along the outer circular arc of the pipe bend, as shown in Figs. 2.

Further, it was found that deformed sheets of plastics film 10 are also inherently stable in the torus sector state when the body is not in the form of a true torus, but of a structure whose curvatures, along the inner and outer arcs (as seen from the axis of the torus or the axis of rotation) do not (at least at the midportion of the body) have the same centres of curvature; instead the centre of curvature 18 of the outside arc 16 is farther from the cores of the torus (pipe axis) than the centre of curvature 22 of the inside arc 20. This is shown, somewhat exaggerated, in Fig. 3a. The relation between the outer arc 16 of the pipe bend - shown in Fig. 3a in a meridional section - and its centre of curvature 18 is the same as in a torus which is constructed according to the strict mathematical sense of word. The inside arc 20, however, is more narrowly curved than the corresponding torus so that its centre of curvature 22 does not coincide with the centre of curvature 18, but is closer to the pipe bend.

The distance between the inside arc 20 and the outside arc 16, calculated along the radii extending from the centre of curvature 18, is less in the centre of the pipe bend (when seen along the pipe axis or core of the torus) then it is at the open ends of the pipe.

Fig. 3b shows a further suitable embodiment of the invention in which the centre of curvature 18' of the outer arc 16' is closer to the core s’of the torus than the centre of curvature 22' of the inside arc 20'.

Pipe bends of the shape illustrated in Fig. 3a are described in German Gebrauchsmuster No. 7,316,667.

They have the advantage that one and the same pipe bend may be used on bends of different shapes and radii of curvature, e.g. L-bends and bends in threaded pipes.

At or near the margins, complementary notches 26a, 26b, 26c, 26d may be provided, for example, so that edges may be hooked together in one or more places either to join the cut edges or to join the bend to an adjacent article as shown by the dotted lines in Figs. and 5. These notches may be produced during cutting or deep-drawing of the sheet of film.

Instead of notches, complementary press studs and depressions may be formed during deep-drawing by means of which the edges 24 may be joined in a form-locking or force-locking manner, as described in the following Figs. 6 to 9.

Fig. 6 shows a snap-fastener type latch member which consists of a, preferably outwardly bent, component 40 in the lower section 41 and a likewise outwardly bent top 42 in the upper section 43.

Fig. 7 shows a simple hooking means consisting of longitudinal doubled-back portions 44 and 45 in the lower and upper sections 41 and 43.

Fig. 8 shows studs 47 which engage depressions 48, which may be wedge-shaped, hooking being effected by the oblique position of the studs (angle a).

Finally, Fig. 9 shows an advantageous embodiment providing dove-tailed, preferably outwardly projecting extensions 50 and 51 which may be tapering. Since the insulating material enclosed by the pipe bend of the invention may possess a certain elasticity, it is possible to distort the pipe bend or sheathing so that the overlapping zones of the sections 41 and 43 are enlarged and one of the dovetailed extensions 50, 51 may be inserted into the other. When the distorting force is released, the dovetailed extensions complementarily engage each other.

The described measures may be accomplished either individually or in any desired combination in a process as defined by the claims. Thus, it is possible, for example, to give the pipe bend the shape illustrated in Fig. 3a and additionally subject it to a thermal after41825 treatment in the closed state and provide latch members.

It will be understood that the above teachings may also be applied to pipe bends for which a shell-type structure corresponding to a torus sector of 180° is deep-drawn and then cut into two parts each of which corresponds to a sector of 90°, although the condition of inherent stability in the closed form is less easily achieved by this method than when an elongated shaped pipe bend component corresponding to a 90° sector, as shown in Fig. 1, is directly deep-drawn.

According to the invention, shaped components of the type illustrated in Fig. la may most advantageously be manufactured by blow molding. In this manner, flasklike structures (Fig. Id) each consisting of two symmetrical components 10 according to Fig. la joined at the edges marked by the numeral 28 are obtained, which are separated from each other by cutting along these edges after the molding process. The manufacture of hollow bodies from extruded plastics films by blow molding is generally known and need not be explained.

Fig. 13 shows a continuous deep-drawing process using a web 30.

Although it is preferred that the pipe bend of the invention be initially made in the form of the shelltype body, it is alternatively possible, and within the scope of the invention, to manufacture shaped pipe bend components which initially correspond to an entire torus and whose shape is produced by cutting a torus along its smallest meridional circle, dividing the torus into appropriate segments, opening the cut edges out until a shaped body with a bulging waist line results, and heattreating the body, as described above.

Claims (23)

1. CLAIMS:1. ' Λ one-piece plastics pipe bend comprising a •iliuol In the shape ol a port ton ol' .1 hollow ring open along its innermost arc, the pipe bend having been formed 5 by bending from an inherently stable (as hereinbefore defined) shell-type body having no re-entrant curves (as hereinbefore defined), the pipe bend also being inherently stable in its portion of a hollow ring conformation.

2. A pipe bend as claimed in claim 1, in which the 10 portion is a 90° sector of the ring.

3. A pipe bend as claimed in claim 1 or claim 2 wherein the pipe bend itself is of substantially circular cross section.

4. A pipe bend as claimed in any one of claims 1 to 15 3, wherein one or both end portions of the sheet terminating in the open edges at the innermost arc are extended so that they overlap in the hollow ring conformation

5. A pipe bend as claimed in any one of claims 1 to 4, wherein the hollow ring conformation has been inherently 20 stabilized by thermal treatment of the sheet material in that conformation.

6. A pipe bend as claimed in any one of claims 1 to 5, wherein the hollow ring conformation is inherently stabilized by a corrugation. 25

7. A pipe bend as claimed in claim 6, wherein the corrugation extends along the outermost arc of the ring.

8. A pipe bend as claimed in any one of claims 1 to 7, wherein the hollow ring conformation is inherently stabilized by forming at least the mid-portion of the outer30 most arc of the ring on a different centre of curvature from that of at least the mid-portion of the innermost arc of the ring.

9. A pipe bend as claimed in claim 8, wherein the centres are such that the radial distance between the innermost and the outermost arcs is less at the midportion of the pipe bend than it is at the ends.

10. A pipe bend as claimed in any of claims 1 to 9, wherein the open edges of the innermost arc are provided with engaging means.

11. A pipe bend as claimed in claim 10, wherein the engaging means are complementary notches.

12. A pipe bend as claimed in claim 10, wherein the engaging means are press studs and complementary depressions

13. A pipe bend as claimed in claim 1, as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.

14. A process for the manufacture of a pipe bend, in which a sheet of plastics film is deformed, by deepdrawing, into a shape which results when a torus sector is cut along its smallest internal circular arc and then opened out until a shell-type body having no re-entrant curves is formed, and the resulting deep-drawn shell-type body is then converted, by bending, to the state of the torus sector by an operation which proceeds inversely to its virtual shaping operation, characterized in that, the body in the state of a torus sector cut open along its innermost arc is subjected to a heat-treatment such that inherent tensions, produced by deep-drawing and bending, are reduced to such an extent that the thermally treated body is inherently stable in the shape of a torus sector and in the shell-type conformation.

15. A modification of the process as claimed in claim 14, wherein the shell-type body is formed by blow molding of a parison rather than by deep-drawing of a sheet.

16. A process as claimed in claim 14, or claim 15, carried out substantially as hereinbefore described. ι1835

17. Α pipe bend whenever made by a process as claimed in any one of claims 14 to 16.

18. A pipe bend as claimed in any one of claims 1 to 13 or claim 17, in the shell-type conformation. 5

19. A method of covering a bend in a pipe which comprises applying a pipe bend, as claimed in any one of claims 1 to 13 or claim 17 in the shell-type conformation, to the pipe, and transforming to the torus sector slate or to the portion of a hollow ring conformation. £0

20. A plastics body that is inherently stable in each of two forms, one form being shaped for covering an elbow in a pipe, and comprising a portion of a hollow ring open along an inner arc, the other form being an open and openended trough having no re-entrant curves, the depth of i5 the central portion of the trough being greater than that of the ends.

21. A process for the manufacture of a body inherently stable both in the form of an open-ended trough having no re-entrant curves, of which the central portion is deeper 20 than the ends, and also in the form of a portion of a hollow ring open along an inner arc in which form it may be used for covering an elbow in a pipe, which comprises forming a plastics sheet into an inherently stable trough form, bending it into the ring form, and heat-treating the body 25 while maintaining it in the ring form to render it inherently stable in that form without depriving it of its inherent stability in the trough form.

22. A process as claimed in claim 21, Wherein the trough form is manufactured by deep-drawing. 30

23. A method of covering a bend in a pipe by installing a body as claimed in claim 20.