GB2257352A

GB2257352A - Flat,one-piece molded part

Info

Publication number: GB2257352A
Application number: GB9213333A
Authority: GB
Inventors: Hermann Bock
Original assignee: BOCK MARTIN KUNSTSTOFF; Martin Bock Kunststoffverarbeitung
Current assignee: BOCK MARTIN KUNSTSTOFF; Martin Bock Kunststoffverarbeitung
Priority date: 1991-07-08
Filing date: 1992-06-23
Publication date: 1993-01-13
Anticipated expiration: 2012-06-23
Also published as: SE9201871L; DK173351B1; NO922649L; DE4122557A1; FI103472B1; FI922818A; FI922818A0; FR2678814B3; FI103472B; SE505330C2; NO301804B1; SE9201871D0; DE4122557C2; FR2678814A1; NO922649D0; GB2257352B; DK87992A; DK87992D0; GB9213333D0

Description

Flat, one-piece molded part 2237SS-2 The invention relates to a flat,

one-piece molded part preferably of injection-molded plastic material with ribs parallel to each other, perpendicular to the surface plane and extending longitudinally in a direction of surface expansion.

Molded parts of the generic kind are used for lots of purposes, for instance for seats, backrest or seat-shell moldings of chairs, largesurface coverings etc.

In particular if the molded part is used as a load-bearing part, it must have a certain bearing capacity and, consequently, stability and flexural rigidity. To improve these qualities it is known to reinforce such molded parts with ribs parallel to each other, perpendicular to the surface plane and extending longitudinally in a surface-expansion direction. However, molded parts thus reinforced cannot be of satisfying stability and flexural strength, since the strength of bending about an axis parallel to the ribs is not or only sightly increased by these measures. Any additional ribs extending in a direction at right angles will improve the flexural rigidity, but they also increase the material consumption and the weight of a molded part thus formed, which may for instance be due to an increase in wall thickness as a measure of stability improvement.

It is an object of the invention to further develop the structure of a flat molded part of the generic kind, such that its flexural rigidity and 0 stability are improved without any substantial increase in material consumption and a comparably low specific weight per unit area being maintained.

This object is attained by a molded part, wherein the moldifig strips located between the ribs are structured as a kind of corrugated profile advancing in the direction of longitudinal extension of the ribs, the corrugated profiles of two neighboring molding strips being arranged in misalignment one relative to the other in the direction of longitudinal 2 extension of the ribs. The molding strips between the ribs being structured as a kind of corrugated profile will fundamentally help to achieve high flexural rigidity homogeneous along the corrugated profile and in a direction at right angles to the longitudinal extension of the ribs. Due to the misalignment of the corrugated profiles of two neighboring molding strips, the two corrugated profiles with their waveshaped area of transition to the ribs bear on a common rib each at different positions in length, which not only improves the flexural rigidity, but also helps to achieve high torsional rigidity.

A further advantage of the embodiment of the molded part according to the invention resides in that the molded part is easily ejectable even after being manufactured in particular by injection-molding.

According to an embodiment of the invention each corrugated profile with its top or bottom side, respectively, is in aligrunent with the top and bottom edges, respectively, of the ribs in the same plane. 'nereby a plane network of contact lines is created on the top and bottom side of the molded part and may be of special use as a bearing or support for further molded parts such as facings or the like to be applied to both sides of the molded part.

According to an embodiment of the invention the misalignment of the corrugated profiles of two neighboring molding strips corresponds to half the wave length of a wave train. This symmetrical misalignment is of particularly favorable effect on the improvement of the flexural and torsional rigidity.

According to a further embodiment of the invention the wave trains of each corrugated profile are each asymmetrically formed in the latters advancing direction, each wave train having both a steeply ascending and a flatly descending flank.

Further embodiments of the invention refer to a molded part, wherein the wall thickness of the molded part is identical in the corrugated profile 2 3 area and in the rib area, and wherein the flexibility of the molded part can be varied by variation of the wave length and/or the wave height and, if necessary, by the rib height in portions of the molded part. These measures clearly reflect that different parameters are available and can be varied for the molded part according to the invention to adjust to desired stability and flexibility properties. Among them are for instance the symmetrical or asymmetrical design of the wave trains of each corrugated profile, the wall thickness of the molded part in the corrugated profile and rib area, the wave length or the wave height and, if necessary, the rib height. Since these parameters are interdependent and may mutually cause different changes in properties, corresponding properties of the molded part and the necessary parameters and shapes of the corrugated profile, respectively, are best determined by tests of variations of the corresponding parameters and shapes.

Another embodiment of the invention relates to a molded part, wherein, if the molded part has a course if necessary bent several times about a neutral axis arranged at right angles to the direction of longitudinal extension of the ribs, the corrugated profiles trace the bending course by correspondingly adapting the angles of inclination between the profile flanks and the top and bottom edges of the ribs. Thereby the molded part may even extend on a course sometimes deviating from its surface plane without losing the desired stability and rigidity properties.

Another embodiment of the invention relates to a molded part, which is used as a seat-backrest shell of a chair with the seat and the backrest forming one piece.

0 Further features, details and advantages of the invention will become apparent from the ensuing description of an example of embodiment and application of the subject matter of the invention taken in conjunction with the annexed figures, in which

Fig. 1 is a part section of a flat molded part according to the invention along the section line I-I of Fig. Z 4 Figs. 2 to 4 are part sections of the molded part along the section lines IMI, 111-111, and IV-IV, respectively, of Fig. 1, Fig. 5 is a diagrammatic section through a seat-backrest shell for a chair, and Fig. 6 is a perspective, plan view of part of the shell of Fig. 5.

The flat molded part illustrated in Figs. 1 to 4 and forming the left part of Fig. 6 is injection-molded in one piece of suitable plastic material and has ribs 3 parallel to each other and perpendicular to the surface plane 2, which extend longitudinally in a direction of surface expansion, i.e. for instance in the longitudinal direction I of the molded part, and of which the cross-section is in the form of a flat rectangle, as seen in Figs. 2 to 4.

The molding strips 4 located between the ribs 3 are structured as a kind of corrugated profile 5 continuing in the longitudinal direction 1 of the ribs 3. As seen in particular in Figs. 1 and 6, the corrugated profiles 5, 5' of two neighboring molding strips 4, 4' are displaced one in relation to the other by the misalignment V in the longitudinal direction 1 of the ribs 3. The misalignment V corresponds to half the wave length L of the corrugated profile 5, so that the corrugated profile 5' of each molding strip 4" following the next is in alignment with the corrugated profile 5 (see Fig. 6).

The top and bottom side of each corrugated profile 5, 5', 5" is flush with the top and bottom edges 6, 7 of the ribs 3 in the same plane. This helps to produce the network 8 of contact lines on the surface 9 of the molded part outlined in Fig. 6, whereby for instance any covering parts applied to it experience optimal support.

As further seen in Fig. 1, each wave train 10 defined by the wave length 1, of each corrugated profile 5, Y, S' is asymmetrically formed in the latter's advancing direction (longitudinal direction 1) by each wave train 10 havina both, a steeply ascending flank 11 and a flatly c descending flank 12. The flanks 11, 12 are straight-lined between the upper and the lower arch portions 13, 14.

Ass further illustrated by Figs. 1 to 4, the wall thickness D of the molded part is about identical in the vicinity of the corrugated profiles 5, 5', 5" and in the vicinity of the ribs 3.

Figs. 5 and 6 represent an example of application for a molded part according to the invention in the form of a seat-backrest shell 15 of a chair with the seat 16 and the backrest 17 made in one piece, the lateral rims of the shell 15 extending in the longitudinal direction I and the upper part of the backrest 17 not being shown in Fig. 6. In the vicinity of the plane of the seat 16 the shell 15 corresponds to the molded part shown in Figs. 1 to 4 as regards the structure of the ribs 3 and the corrugated profiles 5. In a first bending portion 18 and proceeding from the plane of the seat 16 the molded part is bent upwards about a neutral axis 19 arranged at right angles to the longitudinal direction 1 of the ribs, and then, in the course of the backrest 17 and in a second and a third bending portion 20, 21, it extends bent in directions opposite to 0 each other about the two neutral axes 22, 23, which are parallel to the first neutral axis 19. An ergonomically suitable shape of the backrest 17 of the seat-backrest shell is thus achieved. As seen in Fig. 5, the corrugated profiles trace the bending course, the angles of inclination 24 between the profile flanks 12, 13 and the top and bottom edges of the ribs adjusting correspondingly. In the upper bending portion 21 the wave and ribs heights H as well as the wave length L decrease towards the end of the backrest, whereby this portion of the backrest 17 becomes increasingly flexible. Fig. 5 also shows a bottom or rear side facing 25, which covers the full width of the seat-backrest shell downwards and backwards. A lateral rim 26 appears in outlines, through which components (not shown) such as armrests or the facing 25 can be connected with the seat-backrest shell.

6

Claims

CLAIMS:

1. A flat, one-piece molded part of preferably injection-molded plastic material with ribs parallel to each other, perpe.-Lidicular to the surface plane and extending longitudinally in a direction of surface expansion, wherein the molding strips located between the ribs are structured as a kind of corrugated profile advancing in the direction of longitudinal extension of the ribs, the corrugated profiles of two neighboring molding strips being arranged in misalignment one relative to the other in the direction of longitudinal extension of the ribs.

2. A molded part according to claim 1, wherein with its top or bottom side, respectively, each corrugated profile is in alignment with the top and bottom edges, respectively, of the ribs in the same plane.

3. Molded part according to claim I or 2, wherein the misalignment of the corrugated profiles of two neighboring molding strips corresponds to half the wave length of a wave train.

4. A molded part according to one of the afore-mentioned claims, wherein the wave trains of each corrugated profile are each asymmetrically formed in the latter's advancing direction, each wave train having both a steeply ascending and a flatly descending flank.

5. A molded part according to one of the afore-mentioned claims, wherein the wall thickness of the molded part is identical in the corrugated profile area and in the rib area.

6. A molded part according to one of the afore-mentioned claims, wherein the flexibility of the molded part can be varied by variation of the wave length and/or the wave height and, if necessary, by the rib height in portions of the molded part.

7. A molded part according to one of the afore-mentioned claims, wherein, if the molded part has a course if necessary bent several times about a 7 neutral axis arranged at right angles to the direction of longitudinal extension of the ribs, the corrugated profiles trace the bending course by correspondingly adapting the angles of inclination between the profile flanks and the top and bottom. edges of the ribs.

8. A molded part according to claim 7, wherein its being used as a seatbackrest shell of a chair with the seat and the backrest forming one piece.

9. A flat molded part of injection-molded plastics material, substantially as described herein with reference to and as illustrated in the accompanying drawings.