WO1998034064A1

WO1998034064A1 - Pressure vessel and process for making the same

Info

Publication number: WO1998034064A1
Application number: PCT/NO1998/000035
Authority: WO
Inventors: Gaute Jensen
Original assignee: Raufoss Composites AS
Current assignee: Raufoss Composites AS
Priority date: 1997-01-31
Filing date: 1998-02-02
Publication date: 1998-08-06
Anticipated expiration: 1999-07-31
Also published as: NO970451L; NO970451D0; NO307063B1; AU6006798A

Abstract

Method for producing pressure containers for fluids, e.g. propane or butane, comprising the steps of: making a rotational symmetric and fluid tight inner liner (1) of a plastic material, preferably with injection moulding, blow moulding or rotational moulding, with providing of a central opening (20) at one end (the top) of the liner; and winding of the liner with a fibre reinforcement (2) provided with an adhesive and thereafter hardened. A support element is provided, during or after the production of the inner liner (1), in the other end of the liner opposite the first end and axially corresponding to the central opening, said support element (9) including an axially provided centring organ (9A). The liner (1) is mounted for rotation in relation to its axis by cooperation with the central opening (20) and centring organ, a rotation tip or piercer (11, 13) being brought into cooperation with the centring organ (9A), and the mounted liner is rotated for the winding of the fibre reinforcement.

Description

PRESSURE VESSEL AND PROCESS FOR MAKING THE SAME.

Propane bottles and other pressure containers for fluids have been commonly known for many years, based on metal as construction material, in particular steel. These known containers, being to a large extent utilized by people during cabin and outdoor life, have the drawback, inter alia, of being heavy and accordingly difficult to handle. Moreover there is often a problem of knowing how much of the original contents is still left in the bottle or container. Because of the risk of explosion and accidents, many and strict requirements are imposed with respect to such pressure containers. Thus, the safety aspect is very essential in this connection.

In recent years there has been put on the market a propane bottle of composite materials, as described in

Norwegian patent No. 179 423. This known structure is made in part of transparent or translucent materials, these besides being relatively light, so that some of the drawbacks mentioned above regarding pressure containers of steel, are eliminated. The known propane bottle of composite materials however, can not be manufactured in a rational and inexpensive way when the strict safety requirements are to be satisfied, while at the same time preventing damage and accidents as a result of mechanical stresses, such as shock and impact.

In contrast to the manner of manufacturing according to the above Norwegian patent specification, it is particularly advantageous to produce the actual pressure container by first making an inner liner and then winding around it fibre reinforced elements, for example glass fibre bands or treads .

The latter manufacturing method forms the basis of the pressure container being known from Norwegian patent No. 170 552, wherein besides there is described and shown an outer, protective sheath to serve for resisting fire or heat influence. Also, the patent publication describes end elements formed as a top disc and a bottom element, both being secured to the container structure using said fibre winding. The present invention is aimed at a new and improved container construction which to a large degree takes into consideration the conditions during the production, so that the complete containers may be produced rationally and reliably with a high quality on the product. In this context the winding process with fibre strengthening per se is of great importance. The invention also includes a method for producing such pressure containers . The new and inventive features in the method as well as pressure container according to the invention er given in the patent claims . This concerns to a great degree conditions in or around the mentioned inner liner of plastic material, which in the finished product primarily is provided for obtaining fluid tightening. Because of the fibre winding the liner preferably has an rotational symmetry and may be produced by blow-moulding, injection moulding or rotational moulding. It is also advantageous to use such plastic materials both in the liner and in the layer being wound, as the combined structure of the container walls is transparent or translucent. It is also practically suitable to provide a protecting sheath which more or less envelope the pressure container. Such a complete container design is described in the simultaneously filed patent Norwegian patent application No. 97.0449 (PCT/NO98/00026) .

The invention is in the following described referring to the drawings, in which:

Figure 1 shows an example of a pressure container according to the invention mounted on a rotational piercer, in which the fibre winding is considered to be finished, and Figures 2-6 show different embodiments of the supporting elements by the bottom of the pressure container, for use in the fibre winding. Figure 1 shows an axial section of an example of a pressure container during one state of the production process. The wall structure in the container comprises an inner liner 1 having a finished fibre reinforcement or winding in an outer layer 2 covering the cylindrical main body or mid section of the container, as well as the bottom and top sections. On the top (at the left in figure 1) a central opening 20 is shown with a surrounding boss 4, which in use of the pressure container among other thing may serve as a mount for a coupling and valve unit as is known from container e.g. for propane or butane.

The inner liner 1 may be assembled from two or more separate injection moulded parts, which are welded together in a plane marked with 3. Integrated in the liner 1 a reinforcement rib or wall 5 is shown stretching from the bottom construction in the container to through an axial part 5A and further through the welded connection at the plane 3 and to a continuation all the way to the boss 4 on the top of the container. Such ribs or walls 5, 5A lay in principle in radial planes and may be provided in higher or lower numbers, evenly distributed around the circumference of the container. Especially interesting in this relation is a supporting element 9 by the bottom of the container, which plays an important part during the winding process . Depending on the dimensions and extension such a supporting element can have a valuable reinforcement or stiffening effect in the bottom construction, especially in relation to the ribs 5 stretching into and may be fixedly joined to the supporting element .

This supporting element 9 er provided with a centring hole 9A adapted to receive a preferably conical or pointed end 13 on a rotational piercer 11 stretching axially the whole container and out through a holding piece 12 mounted in the boss 4. By 10 it is in a general way illustrated a machine or production equipment performing or aiding the mentioned winding on the outside of the liner 1. In figure 1 the winding is supposedly finished, as the resulting outer layer 2 is in place. The winding process per se may be of any known type, and needs no further explanation here. An important point in this context is, however, that with the described support of the liner 1 on the piercer 11 it may, using the machinery 10 set the liner into the required rotary motion for the winding to be performed. The fibre reinforcement being winded on may in a known way be provided with an adhesive which thereafter is allowed to harden. The hardening may advantageously be performed using heat treatment in a subsequent operational step, as the fibre winding may be done in a cold or warm condition. According to the invention it is also preferred to provide a inner overpressure in the liner before and during the winding. With the shown and described support such pressurizing is relatively easily obtained.

The support for winding as shown in figure 1 may according to the invention also be exploited for a precise length calibration of the liner 1 while this is somewhat deformable. This is done by adjusting the length of the piercer slightly, so that a stretching force between the bottom construction with the supporting element 9 and the top section of the container with the boss 4. What may be obtained with this method is a certain lengthening of a slightly too short liner 1 in the axial direction, all of the produced liners thus being calibrated to the exact same axial length. This length calibration should preferably be performed before the actual winding of the layer 2.

Another advantageous use of the supporting arrangement in figure 1 is the use of the piercer 11, with ancillary holding device 12 and possibly a moveable equipment unit 10, to transfer the enwrapped container 1,2 from the winding station to a subsequent operation step, e.g. a hardening step as mentioned above.

Figure 1 shows an example of an embodiment of the support element 9 with ancillary centring organ shaped as a conical hole 9A. As alternatives to such an embodiment the figures 2-6 illustrates other possibilities, each under different conditions being advantageous when producing different pressure containers. Figures 2 and 3 show support elements 29 and 39, respectively, being integrated parts of the corresponding liner, the liner in these embodiments preferably being produced by injection moulding. Figure 2 shows the previously mentioned rib or supporting wall 5 and also the outer, winded layer 2. The support element 29 is, the same way as the element 9 in figure 1, produced inside the liner 1, and has a centring hole 29A which may be threaded in order to cooperate with the corresponding end part of the rotation piercer with corresponding threading. This ensures the fastening of the support element and thus the whole liner for the winding process.

While figure 2 and figures 4, 5, and 6 are based upon a centring organ in form of a hole, the alternative in figure 3 is based upon an integrated support element 39 extending out into a conical point or tip 39A adapted to cooperate with a rotation piercer having a complementary, cup-shaped end part adapted to lay on the outside of the conical tip 39A.

Figures 2 and 3 show the support elements 29 and 39 inside the liner 1, but in figure 4, 5 and 6 support elements are shown being positioned outside the liner l. This means that the rotational piercer or spindle is not brought into the inside of the liner 1, but axially from outside (i.e. from the right in these three figures) . These outer support elements 49, 59, and 69 are fastened to the pockets 48, 58 and 68, respectively, in the corresponding liner.

The support element 49 in figure 4 has a relatively deep plug-shaped form with a conical hole 49A. The winded layer 2 also have in the finished pressure container a corresponding hole 42, possibly as a direct result of the winding being performed completely against the end part of the rotation piercer in this area. The hole-combination 49A-42 in the bottom construction of the container does not represent a weakness or any other disadvantage in the resulting product.

The example in figure 5 has a relatively large resemblance to the one in figure 4, but the support element 59 has somewhat less depth and has a cylindric hole 59A with threads, corresponding to the hole and the threads 29A in figure 2. Also the outer part 52 of the hole is in the winded layer 2.

At last figure 6 shows a more plate-shaped support element 69, than the plug-shaped elements in figures 4 and 5. The pocket 68 in the liner 1 is correspondingly relatively wider in the radial dimension, but is, similar to the pockets 48 and 58, connected to or integrated in the support ribs 5. To what degree such an integrated structure is preferable and suitable for rational production depends also on how the liner 1 as a whole is produced. The examples in 4,5 and 6 are primarily based upon production of the liner using blow-moulding or rotational moulding.

The holes 62 and 69A in figure 6 have shapes corresponding completely to the holes 42 and 49A in figure 4. For suitable transferring of rotational momentum from the cooperating piercer or tip, the holes shown in figures 2, 4, 5 and 6 have either inner threading as mentioned above or a profiled or edged shape securing rotational coupling to the piercer. It may also be correct to have a rotational locking between the supporting elements in the embodiments in figures 4, 5 and 6. This type of locking may suitably be provided by giving the elements 49, 59 and 69 a basic shape being not completely rotational symmetric, e.g. polygonal, and the corresponding pockets receiving these elements having a complementary shape. A special variant of such a rotational locking is shown in figure 6, where the pocket 68 and the element 69 both may essentially have rotational symmetry, but by 66 a recessed segment in the supporting element 69 is shown, as the recess, after positioning of the element 69 in the pocket 68, is filled with e.g. a suitable adhesive to obtain the here described locking.

Regarding the geometrical shapes being illustrated for the supporting elements in the drawings a common feature is that the outer main surfaces stretches essentially in line with the adjacent outer surfaces of the liner 1. This is among other things preferable since it is a great advantage if the fibre reinforcement layer 2 covers essential parts of the outer surfaces of the support elements. Thus a good anchoring of the elements is secured. These have, in addition to their supporting function during production, also a reinforcing effect in the bottom construction of the finished pressure containers . This advantageous effect may be of great value even if the supporting element comprises a relatively small part of the total surface area of the bottom construction of the containers . The embodiment in figure 2, and partly in figure 3, is very advantageous in relation to this reinforcing effect. It is therefore suitable as illustrated in figure 2, that the liner has a gradually increasing wall thickness in a part surrounding the supporting element 29, so that this provides good reinforcement .

The supporting elements in figures 4, 5 and 6 are produced separately before the enclosing of the respective pockets 48, 58, 68. The elements may be made from metals or similar material being stronger than the material in the liner 1.

Claims

C l a i m s

1. Method for producing pressure containers for fluids, e.g. propane or butane, comprising the steps of: making a rotational symmetric and fluid tight inner liner (1) of a plastic material, preferably with injection moulding, blow moulding or rotational moulding, with providing of a central opening (20) at one end (the top) of the liner, and winding of the liner with a fibre reinforcement (2) provided with an adhesive and thereafter hardened, c h a r a c t e r i z e d in that a support element is provided, during or after the production of the inner liner (1) , in the other end of the liner opposite the first end and axially corresponding to the central opening, that said support element (9) includes an axially provided centring organ (9A) , that the liner (1) is mounted for rotation in relation to its axis by cooperation with the central opening (20) and centring organ, a rotation tip or piercer (11,13) being brought into cooperation with the centring organ (9A) , and that the mounted liner is rotated for the winding of the fibre reinforcement.

2. Method according to claim 1, c h a r a c t e r i z e d in that the liner (1) is provided with an inner overpressure before and during the winding.

3. Method according to claim 1 or 2 , c h a r a c t e r i z e d in that the support element (9,29,39) with the centring organ (9A,29A,39A) is provided substantially inside the liner (1) , and that the rotational piercer (11) extends through the central opening and the rotational piercer at same time cooperating with the central opening .

4. Method according to claim 3, c h a r a c t e r i z e d in that the inner liner (1) with enwrapped fibre reinforcement (2) and still mounted on the rotational piercer (11,12,13), is transferred and subjected to at leat one subsequent production step, especially a hardening step.

5. Method according to one of the claims 1-4, c h a r a c t e r i z e d in that the boss part (4) is positioned in the central opening (20) before supporting the liner for winding.

6. Method according to one of the claims 1-5, c h a r a c t e r i z e d in that the centring organ is made as a hole (9A, 29A, 49A, 59A, 69A) in the support element (9,29,49,59,69) .

7. Method according to one of the claims 3, 4 or 5, c h a r a c t e r i z e d in that the centring organ is formed as a slightly pointed end part (39A) on the support element (39) .

8. Method according to one of the claims 3 or 5, c h a r a c t e r i z e d in that said mounting using the boss part (9) is used to precisely calibrate the length of the liner (1) while it is slightly deformable, preferably prior to the winding.

9. Method according to one of the claims 1-6, c h a r a c t e r i z e d in that the support element (49,59,69) with the centring organ provided as a hole (49A, 59A, 69A) produced substantially on the outside of the liner (1) , and that parts of the winding is positioned close up to the mentioned rotational tip or piercer in the area surrounding the hole in the support element .

10. Pressure container for fluids, e.g. propane and butane, comprising a rotationally symmetric and fluid tight inner liner (1) of plastic materials, preferably produced by injection moulding, blow-moulding or rotational moulding, and with a central opening (20) by the first end of the liner, and a winded fibre reinforcement provided as an outer stress relieving layer (2) on the outside of the liner (1) , as well as a relatively rigid element (9) provided in the second end of the liner, c h a r a c t e r i z e d in that the element constitutes a support element (9) provided with an axially arranged centring organ (9A) for use in centring and mounting purposes, especially during the winding with fibre reinforcement, and that the outer surface of the support element (9) is substantially in line with the adjacent outer surface of the liner (1) .

11. Pressure container according to claim 10, c h a r a c t e r i z e d in that the support element (9) constitutes a relatively small part of the surface area of the bottom construction.

12. Pressure container according to claim 10 or 11, c h a r a c t e r i z e d in that the centring organ forms a hole (9A,29A,49A, 59A, 69A) in the support element (9).

13. Pressure container according to claim 10, 11 or 12, c h a r a c t e r i z e d in that the fibre reinforcement (2) substantially covers the outer surface of the support element (9,29,49,59,69) for secured anchoring of this.

14. Pressure container according to claim 12 or 13 , c h a r a c t e r i z e d in that the hole (9A,29A,- 49A,59A,69A) in the support element is formed with a profiled circumference and possibly at least partially conical (49A,69A).

15. Pressure container according to claim 12 or 13, c h a r a c t e r i z e d in that the hole (29A,59A) in the support element includes threads.

16. Pressure container according to one of claims 10-15, wherein that the inner liner is produced by injection moulding, c h a r a c t e r i z e d in that support ribs (5) are provided on the inside of the liner stretching integrated in the liner walls mainly between central parts by the two ends and with intermediate, substantially axial parts (5A) , and that the support element (9,29,49,59,69) is strengthened by at least some of the ribs (5) .

17. Pressure container according to one of the claims 10- 15, c h a r a c t e r i z e d in that the liner (1) has an increase wall thickness in a part surrounding the support element (29) for reinforcing it.

18. Pressure container according to one of the claims 12- 17, c h a r a c t e r i z e d in that the support element (49,59,69) with its hole (49A, 59A, 69A) is positioned substantially on the outside of the liner (1) .

19. Pressure container according to claim 18, c h a r a c t e r i z e d in that the support element (49,59,69) is produced separately and positioned in a pocket (48,58,68) prepared in the liner (1).

20. Pressure container according to claim 19, c h a r a c t e r i z e d in that the support element (69) substantially has a plate shape.

21. Pressure container according to claim 19, c h a r a c t e r i z e d in that the support element (49,59) has a substantially plug-like shape, possibly with a more or less conical part.

22. Pressure container according to claim 19, 20 or 21, c h a r a c t e r i z e d in that the support element (49,59,69) is made from a metal or similar material being more rigid than the material in the liner.

23. Pressure container according to one of the claims 19- 22, c h a r a c t e r i z e d in that the support element (69) is rotationally locked (66) in the corresponding pocket (68) .