WO1988009732A1

WO1988009732A1 - A blow moulded bumper and a method for its manufacture

Info

Publication number: WO1988009732A1
Application number: PCT/SE1988/000293
Authority: WO
Inventors: Mikael Quasters
Original assignee: Plm Ab
Priority date: 1987-06-05
Filing date: 1988-06-02
Publication date: 1988-12-15
Also published as: SE8702342D0; SE8702342L

Abstract

A bumper (1) comprises a body (10) which is connected to a supporting element (20a) oriented in longitudinal direction of the bumper. The supporting element (20a) is provided with one or more connecting means (21) for the attachment of the bumper to a vehicle. The body (10) is constituted of a blow moulded body of thermoplastic material which extends along the bumper from its one end to its other end. The blow moulded body includes at least one cavity (11) whose boundary wall (14a) is connected by fixing means (24) to the supporting element (20a) for the attachment of the body (10) to the same. A method for the manufacture of the bumper is also disclosed wherein the supporting element (20a) is introduced into a blow mould (40) to form a part of the surfaces of the blow mould. A tubular parison of thermoplastic material is expanded against the mould surfaces and the body thus formed attaches to the supporting element by fixing means and/or adhesive provided on the supporting element.

Description

BLOW MOULDED BUMPER AND A METHOD FOR ITS MANUFACTURE

The present invention relates to a bumper for vehicles and a method for manufacturing the same in accordance with the preambles to claims 1 and claim 8, respectively.

Known arrangements comprising bumpers of a design in accordance v/ith what has been said in the preceding paragraph are relatively compli¬ cated to produce, since they consist of many parts which are assembled to form the finished bumper. This means a complicated and thus expensive technique, since each component has to be manufactured separately and subsequently joined together with the remaining components during the assembly of the bumpers.

In the field of vehicles a technique has started to be used to an increasing extent in recent times where for the improvement of the air flow around a vehicle a so-called spoiler is connected to the bumper. The assembling takes place- in a separate assembly step and as a rule after the bumper has been fixed to the vehicle. In addition to this, frequently, rear inspection screens and so-called flukes (side pieces) occur which likewise are connected to the bumper of the vehicle and are assembled separately. Spoiler, rear inspection screen and side pieces also consist of a number of units which are successively fixed to one another and to the bumper or the vehicle.

To achieve an acceptable finish of the combination of the bumper and its complementary items (spoiler, rear inspection screen, side pieces) it is necessary to design the units so that any dimensional deviations between them do not involve the occurrence at the transition between the bumper and e.g. the spoiler or the body of e.g. cracks or close fits which impair the visual impression and thereby the impression of quality, which the producer wishes the prospective customer to experience. The present invention relates to a bumper and a method for manu¬ facturing the same where the above-mentioned disadvantages are avoided. It is a particularly valuable feature of the present invention that it makes possible a rational manufacture of the bumper and, if the case arises, of its connected elements such as end flukes, rear inspection screen and spoiler. Thanks to the simplified method of manufacture, the costs of the manufacture of the bumper as well as of the assembly of the same, and also of elements connected to the bumper are reduced, at the same time as the dimensional accuracy and the fit between the units and the connection of the units to the body are improved.

The novelty of the bumper in accordance with the invention and the new method for producing the bumper are indicated in the charac- terizing part of claim 1 and in the characterizing part of claim 11, respectively.

In accordance with a preferred embodiment of the invention the blow-moulded body of plastic material comprises a substantially downwards directed part, arranged in longitudinal direction of the bumper and assembled with the bumper on a vehicle, which forms a spoiler or a rear inspection screen. The downwards directed part is substantially hollow and forms one or more cavities.

In one embodiment the blow-moulded body forms in both the end regions of the bumper portions which are oriented at an angle to the longitudinal axis of the bumper. These portions are designed as side protection (end flukes).

In a further embodiment opposite walls of the bumper are joined to one another in a region where the downwards directed part connects to the remainder of the bumper. As a result the downwards directed part forms a separate cavity which independently of the cavity of the bumper can be filled with a flexible material, e.g. foamed plastic material, should this be desired.

Because opposite walls of the bumper are joined to one another where the downwards directed part connects to the remainder of the bumper, it is made possible also to design the connection region so that the downwards directed part can have a certain mobility therein, as a result of which damaging effects on the downwards directed part in conjunction with minor collisions with hard sr?.ow or ice banks, animals etc. may be reduced.

In accordance with yet another preferred embodiment of the invention, in each blowing process a dimensionally stable supporting element is placed in the blow mould prior to the expanding of the material. This supporting element forms in the cavity of the blow mould a boundary surface which constitutes part of the walls of the blow mould. The supporting element, moreover, in certain embodiments, is provided with mechanical elements which have the effect that on expansion of the parison the hollow body is fixed to the supporting element.

Alternatively, or complementarily, the supporting element is coated with an adhesive which, as the parison is expanded against the wall of the blow mould, forms a connecting element in the form of a glue line between the hollow body and the supporting element.

Further appropriate embodiments of the invention are described in the dependent claims.

The invention is described in greater detail in connection with a number of Figures, wherein

Fig. 1a. lb show sections through alternative embodiments of a blow mould with a parison placed in the blow mould

Fig. 2a, 2b show sections corresponding to Fig. 1a, lb after expansion of the parison, Fig. 3 shows a section through a bumper with spoiler in accordance with a first embodiment,

Fig. 4 shows a section through a bumper with spoiler in a second embodiment,

Fig. 5 shows the bumper seen from the top,

Fig. 6 is a front view of the bumper

Fig. 7 is a side view of the bumper.

In Figures la, lb and 2a, 2b embodiments of a blow mould 40 are shown consisting of two mould parts 43, 44 which by driving means (not shown in the figures) are movable to and from a working position wherein the mould parts form a substantially closed cavity 42 composed of two partial cavities 41a and 41b, respectively which are separated by a transition region 48 wherein the mould surfaces 42 of the mould cavity 41 are located closely adjoining one another. The transition region forms a connection between the two partial cavi¬ ties. One mould part 43 in the embodiments shown is provided with means for the insertion of a supporting element 20a, 20b which is to be incorporated in the product to be manufactured in the blow mould. Although in Fig. la, lb the supporting element is shown with refe- rence to particular embodiments, the mould part 43 may be arranged so in other embodiments, of course, that it can accept supporting elements of different designs. It is evident from the Figures that the supporting element forms a portion of the mould surfce 42 of the cavity 41. In the embodiment shown in the Figures, la, 2a the supporting element 20a forms one of the opposing mould surfaces 42 in the transition region 48. The supporting element as a rule is constituted of aluminium, but supporting elements of plastic mate¬ rial, preferably reinforced plastic material, are used in certain appliations. Ducts 49a, 49b for heat transfer medium are provided in the two mould parts 43, 44. In Fig. la, lb is shown, moreover, a tubular parison 50 which extends along the whole length of the mould cavity. In Fig. 1a the distance between the opposing mould surface 42 in the transition region 48 is sufficiently great for the inner boundary surfaces of the tubular parison to be separated in the transition region of the mould, whereas Fig. 1b shows an embodiment where on movement of the mould parts to their working position the inner boundary surfaces of the parison are made to lie against one another in the transition region of the mould. The region of the parison which corresponds to the transition region of the mould is designated connecting region and has the reference numerals 15a and 15b, respectively. In Fig. la is also shown how in certain embodiments an adhesive 25, such as a glue, is applied to the mould surface 42 of the supporting element.

In Fig. 2a, 2b are shown alternative embodiments of a hollow body 10a and 10b, respectively, which is formed after the tubular parison 50 by means of blow moulding has been expanded against the surface 42 of the blow mould. In the embodiment shown in Fig. 2a the hollow body 10 forms a closed cavity composed of a first cavity 11 and a second cavity 13, the second cavity being situated in a part 12 which in the Figure is directed substantially downwards. Reference numerals 14a, 14b indicate substantially opposing walls of the hollow body 10. In accordance with the embodiment in Fig. 2b the two cavities 11 and 13, respectively, form cavities separated from one another. In both embodiments a connecting region 17a, 17b exists between the two cavities which corresponds to the connecting region 15a, 15b of the parison and which on moulding of the bumper is formed in the area of the transition region 48 of the blowing mould. The hollow body 10 together with the supporting element 20a, 20b forms the bumper 1. In certain embodiments the cavities 11 and 13, respectively, are divided into several partial cavities or compartments.

In the Figures 3 and 4 which show cross-sections of embodiments of the bumper 1 is found again the hollow body 10 of plastic material. The hollow body is shown in embodiments corresponding to those in Fig. 2a, 2b, that is to say comprising the part 12 directed downwards in the Figures which forms a spoiler, alternatively forms a so-called inspection screen when it is included in a rear bumper. The upper cavity of the hollow body as a rule is filled with a flexible, resilient and energy-absorb ng material 30, e.g. foamed plastic material, preferably polyurethane foam. In certain applications the lower cavity too is provided with a filling of foamed plastic material 31. As is evident from the Figures the two cavities 11 and 13, respectively, are del mited from one another (se also Fig. 2a and 2b) owing to the opposing walls 14a, 14b in the connecting region 17a, 17b being situated closely adjoining one another, as is shown in Fig. 3, or joined to one another, as is shown in Fig. 4.

The hollow body 10 is joined to the largely dimensionally stable supporting element 20a, 20b. The supporting element is provided with connecting means 21, 22 for the attachment of the supporting element, and thus the bumper, to a vehicle. In certain applications the connecting means 21 consist e, g, of brackets which are fastened with screws to the vehicle whilst in other applications the connecting means 22 consist of undercuts which co-operate with arrangements corresponding thereto on the vehicle. The embodiment of the connecting means 22 shown in Fig. 4 implies also that it will constitute a projecting means 23 which is matched on the hollow body 10 by an undercut 16. The projecting means 23 and the undercut 16 co-operate so as to fix the hollow body to the largely di ensionally stable supporting element 20b. In certain embodiments this connection is replaced by a glue line 24, such as shown in Fig. 3, whilst in other embodiments the glue line constitutes a complement to the aforementioned attachment betv/een the projecting means and the undercut 16.

Fig. 5-7 show in addition to v/hat is evident already from the earlier Figures, that the bumper in certain embodiments terminates at both ends 18a, 18b in portions 19a, 19b which form angles to the longi¬ tudinal direction of the bumper. When the bumper is assembled on the vehicle these portions constitute side protection for the same. In certain embodiments the side protections form cavitites which are connected to the upper cavity 11 shown in the Figures, whilst in other embodiments the cavities of the side protections are separated from the upper cavity of the bumper. To enhance the mechanical strength of the side protections, the cavities in the side protec¬ tions too are filled with foamed plastics, In these embodiments the upper cavity 11 of the bumper and the cavities of the side protection as a rule form a coherent cavity.

In the manufacture of the bumpers a tube is extruded and is enclosed ■ by the blow mould. During the extrusion a slightly elevated internal pressure is imparted to the tube which makes it posssible that on closure of the mould by means of the surfaces 42 of the mould, and especially by using the mould surfaces in the transition region 48, the material in the tube is distributed as shown in principle in Fig, 1a or b, that is to say so that the two partial cavities 41a, 41b are provided with sufficient material so that the wall thickness of the hollow body, which is formed in the subsequent blowing, gives the necessary mechanical stability to the same. As shown in the Figures, the dimensionally stable supporting element 20a, 20b is inserted as a rule into the blow mould and forms part of the boundary walls of the blow mould, whilst in other embodiments the blow mould is provided with mould walls whose configuration corresponds to the final form of the hollow body 10. After the parts of the blow mould have been moved to the moulding position, that is to say the blow mould has been closed, the pressure inside the parison is increased further with the help of one or more blow mandrels which are introduced into the hollow space 41 or partial hollow spaces 41a, 41b, and the parison is expanded to engage the mould surfaces of the blow mould.

In certain embodiments (see Fig. 1b) the moulding of the hollow body 10 is started in that, as the mould parts are moved to the working position, the walls of the tubular parison are pressed towards one another by the mould surfaces 42 in the transition region 48 of the mould, and since they still are at high temperature, they will then as a rule be fixed to one another in a region corresponding to the connecting region 15a, 15b of the parison and thereby form the connecting region 17a, 17b of the hollow body 10.

After the material in the hollow body generally has undergone a certain cooling, the tip of an injection needle is introduced through the material wall and a plastic material, suitable for foaming, is injected by means of the injection needle into the hollow body 10. The interior of the hollow body is still at a sufficiently high temperature for the desired foaming to take place. In certain cases the injection needle is introduced into the hole which is formed when the blow mandrel is withdrawn from the material wall.

Since the distance between the opposing walls in the connection regions 17a and 17b, respectively, is extremely small or alter¬ natively, as shown in Fig. 4, the walls are joined to one another, it will be as a rule only the cavity 11 which is filled with foamed plastic material 31. In certain cases, where the cavity 13 in the lower part 12 too is to be filled with foamed plastic material, the distance between the opposing walls in the connecting region 17 is made a little larger, or alternatively a further injection needle is provided which penetrates the wall 14 of the hollow body 10 in the region of the lower part 12 in order to introduce foamed plastic material into its cavity 13. In cases where the cavities of the side protections are to be provided with foamed plastics, this is done either by introducing separate injection needles into the cavities of the side protections or by providing a direct connection between the upper cavity 11 of the bumper and the cavities of the side protec¬ tions so as to allow these to be filled with foamed plastics which is introduced via the upper cavity.

The invention has been^' described in the foregoing in conjunction with a number of Figures which show embodiments of the invention where the bumper includes a downwards directed part suitable to constitute a spoiler or a rear inspection screen. It will be obvious to those versed in the art, however, that the concept of the invention as such also embraces an embodiment where such a downwards directed part is missing.

In certain embodiments, as shown in Fig. 1a, the dimensionally stable supporting element is coated with an adhesive 25 against which the plastic material of the parison is expanded. The expanded plastic material is still relatively warm when it makes contact with the adhesive and is pressed against the same owing to the pressure inside the parison. As a result of this an extremely strong joint 24 (glue line) is achieved between the dimensionally stable supporting element and the hollow body 10.

The foregoing detailed description has made reference only to a limited number of embodiments of the invention, but it will be readily appreciated by those versed in the art that the invention embraces a great number of embodiments within the scope of the following claims.

Claims

1. A bumper (1) comprising a body (10) which is connected with a supporting element (20a, 20b) oriented in longitudinal direction of the bumper which is provided with one or more connecting means (21, 22) for the attachment of the bumper to a vehicle, c h a r a c t e r i z e d in that the body (10) is constituted of a blow-moulded body of thermoplastic material, said body extending along the bumper from its one end (18a) to its other end (18b), and that the blow-moulded body includes at least one cavity (11, 13) whose boundary wall (14a) is connected by fixing means (23, 24) to the supporting element (20a, 20b) for the attachment of the body (10) to the same.

2. A bumper (1) in accordance with claim 1, c h a r a c t e r¬ i z e d in that the blow-moulded body (10) is the two end regions (18a, 18b) of the bumper forms portions (19a, 19b) oriented at an angle to the longitudinal direction of the bumper which assembled on the vehicle with the bumper constitute side protections for the same and/or that the hollow body (10) of plastic material has, in longitudinal direction of the bumper and assembled on a vehicle with the bumper, a downv/ards directed part (12) forming a spoiler or a rear inspection screen.

3. A bumper (1) in accordance with claim 2, c h a r a c t e r¬ i z e d in that the downwards directed part (12) is substantially hollow and forms at least one cavity (13) and/or that the walls (14a, 14b) of the bumper are joined to one another in a connecting region (17) where the downwards directed part connects to the remainder of the bumper.

4. A bumper (1) in accordance v/ith anyone of claims 1-3, c h a r a c t e r i z e d in that at least the cavity or cavities (11) whose boundary wall is joined by fixing means (23, 24) to the supporting element (20a, 20b) is/are filled with a flexible, resilient and energy-absorbent material (30), e.g. foamed plastic material (31).

5. A bumper (1) in accordance with anyone of the preceding claims, c h a r a c t e r i z e d in that the supporting element (20a, 20b) consists of plastic material, preferably a reinforced plastic material.

6. A bumpber (1) in accordance with anyone of the preceding claims, c h a r a c t e r i z e d in that the supporting element (20a, 20b) and the hollow body (10) are attached to one another by means of one or more glue lines (24) and/or that the supporting element (20a, 20b) and the hollow body (10) are attached to one another through one or more undercuts (16) arranged on the hollow body (10) and embracing projecting portions (23) of the supporting element.

7. A bumper (1) in accordance with anyone of the preceding claims, c h a r a c t e r i z e d in that the connecting means (22) of the supporting element (20b) are formed by undercuts.

8. A method for the manufacture of a bumper (1) which comprises a hollow body (10a, 10b) and a largely dimensionally stable supporting element (20a. 20b), where the body is connected to the supporting element and where the supporting element forms one or more connecting means (21, 22) for the attachment of the bumper to a vehicle, c h a r a c t e r i z e d in that the supporting element (20a, 20b) is introduced into a blow mould (40) comprising at least two parts (43, 44) so as to form in the cavity (41) of the blow mould a part of the surfaces (42) of the blow mould, that the hollow body (10a, 10b) is formed with at least one cavity (11, 13) by the blowing of a substantially tubular parison (50) of thermoplastic material to expand to abut against the mould surfaces (42) of the blow mould and that the supporting element (20a, 20b) is provided with projecting fixing means (23) and/or is coated with an adhesive (25) which has the effect that on expansion of the parison against the surfaces (42) of the blow mould said means or said adhesive form means of attachment for the fixing of the body (10a, 10b) to the supporting element.

9. A method for the manufacture of a bumper in accordance with claim 8, c h a r a c t e r i z e d in that a plastic material (31) suitable for foaming is introduced by means of one or more dies into the interior of the hollow body (10a, 10b) and is maintained there at a temperature suitable for foaming of the material, at least one of the cavities (11, 13) being filled with foamed material.

10. A method for the manufacture of a bumper (1) in accordance with claims 8 or 9, c h a r a c t e r i z e d in that prior to the expansion of the tubular parison (50) the parts of the mould (43, 44), on movement towards one another for the purpose of closing the blow mould (40), distribute the material of the parison beween a first partial cavity (41a) of the blow mould and a second partial cavity (41b) of the blow mould are separated by a transition region (48) where the moulding surfaces of the mould walls are adjoining one another, and that in the second partial cavity (41b) a part (13) extending in longitudinal direction of the bumper is formed which projects from the remaining part of the hollow body.

11. A method for the manufacture of a bumper (1) in accordance with claim 10, c h a r a c t e r i z e d in that whilst the walls of the parison (50) are at a high temperature at least in a connecting region (15b) the walls are pressed against one another by the mould surfaces (42) in the transition region (48) to cause joining of the walls to one another in the said region.