GB2209702A

GB2209702A - Moulding grooved articles

Info

Publication number: GB2209702A
Application number: GB8821440A
Authority: GB
Inventors: Ryuetsu Oikawa; Akihiko Fujita; Satoshi Kawarazaki
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 1987-09-14
Filing date: 1988-09-13
Publication date: 1989-05-24
Anticipated expiration: 2008-09-13
Also published as: JPS6472821A; GB8821440D0; GB2209702B; DE3831274C2; DE3831274A1

Description

M INJECTION MOLDED ANGLE PRODUCT

BACKGROUND OF THE INVENTION

2209702 Field of the Invention

The present invention relates to an injection molded angle product, more specifically to an improvement in molding precision of angle products.

Description of the Prior Art

Fig. 1 shows a channel-shaped injection molded product by way of example of angle products. A channel-shaped product 20 is formed with a bottom wall portion 10 and two side wall portions 20 connected at both corner portions P of the bottom wall portion 10. This channel-shaped product 20 can be formed through a single step by inje.;tion molding a thermoplastic resin so that the wall thickness r thereof can be formed-uniformly.

To mold a precise channel-shaped product, an -injection molding die is usually formed so that the angles subtendc--,--- by the bottom wall 10 and the two side walls -20 are at right angles or the channel width is Lmm at the two top ends of the two side walls as shown in Fig. 2 (A) In ti--prior-art channel-shaped injection molded products, however, there exists a problem in that both the side walls are tend to be included inward or the channel width is reduced to imm at the two top ends of the two side walls, after the injection molded products have been removed from a die for cooling or hardening the molded thermoplastic resin. The above-mentioned problem will arise in the sam2 way in other injection molded anqle products such as L-shaped products.

The inventors have studied the reasGn injection mc-lided ancle _are direction after having been re7c-,,-e(2 E:--or. a 1 - or hardening, and clarified the causes thereo-'. will be described hereinbelow with reference to (B) and (C).

(1) After the product has been re,-,iovei; frc,,. a d J. e the bottom wall 10 and the side wall 20 are bi;'L-',i cool-e:,2 uniformly beginning from both the inner and outer surfaces I and 0 tgereof as shown by hatched portions in Fig. 3 (A) (2) However. the wall thickness at the corner portion R is thicker than that of the other wa 1 ls 1 the cross-hatched portion 10 is cooled lastly as shosin in Fig. 3(B).

(3) Therefore, when the cross-hatched portion 10 is. cooled or hardened, a contraction force is generated at the corner portion R in arrow directions A and B as shown in Fig. 3(C), so that the side wall 20 is deformed or incl-ir-)c--3 toward the bottom wall 10 and therefore an angle subtended by the two walls 10 and 20 is reduced.

m F THE INVENTION SUMM" RY O'L 22 -0 With these problems in mind, therefore, -is.

primary object o f the present inventi.on to provide injection molded angle product in which angles subtended two walls of the product will be kept unchangeld even after the product has been removed from an injection molding die Lor cooling or hardening.

To achieve the above-mentioned object, an injection molded angle product formed with at leas' two walls is characterized in that a groove is formed along and; in the- vicinity of a corner portion between two walls. The groove is formed preferably along an inner edge portic.n between the two walls. The groove is preferably U-shaped in cross se---,'L,-.ion.

-shaped are 10 he width and depth of the U 60% o.-- a wall thickness of the angle 2 1 I.

- ---------- P100P, (JUALITY is i)re-'L:erable to form the angle nl---c)iuc1- 21 reinforcing ribs arranged at re,:-:) ar across tl e croove so as to connect the Iwo C -- BPIEF DESCRIPTION OF THE

The 'features and advantages of the injection molded angle product according to the present invention will be more clearly appreciated Irom the following description taken in conjunction with the accompanying drawings in which like reference numerals designate the same or similar elements throughout the figures thereof and in which:

Fig. 1 is a perspective view showing a channel-shaped injection molded product as an example o= imection molded angle products; Fig. 2(A) is a cross-sectional view te-en along the line II(A)-II(A) shown in Fig. 1; Fig. 2(B) is a similar cross-sectional view of the same cooled product; Fig. 3(A), (B) and (C) ar-e f-?-agmen-Lar,,7 views of an angle product, for assistance 2-n explaining. the reason why the side wall is bent inward; Fig. 4 is a perspective view showing a channel-shaped injection molded product of the present invention; Fig. 5(A) is a cross-sectional view taken along the line VW-V(A) shown in Fig. 4; and Fig. 5(B) is an enlarged cross-sect-ional view for assistance in explaining the effect of the present invention.

3.0 DETAILED DESCRIPTION OF THE PREEERRED EME'3DIMENTS

An embodiment of inje--t-J--n molded -crolu.,--t present- invention will be described here i -belc,,, with reference to el 3 FiQ. 4 shows a channel-shaped injec-'--j.-,-i E by way of example of angle products. Th product E is formed with a ottom wall.10 a: 3 C----:) sJIG walls 20 having substantially the sairie wall tr and made of a thermoplastic resin by injection moldinp process.

In F19. 4, the feature of the channelshaped injectioj, molded product E is additionally formed with two grooves 30 along and in the vicinity of corner portions R or inner edge portion K between the bottom wall 10 and the two side walls 20 and a plurality of reinforcing ribs 40 arranged at regular intervals across each groove 30 so as to connect the bottom wall 20 to the side wall 20.

The presence of the grooves 30 serves to allo,,,i the material near the groove 30 or near the ed--, portion between the two walls to be cooled more rapicily than -'L-h,-:

bottom wall 20 and the side wall 10 asdepicted by the hatched lines in Fig. 5(B). Therefore, it is possible -,.-o e-f-.;"ectively prevent a contraction force r 0-, b. c i generated at the corner portion R, thus it being to securely keep the angles subtended by the bottor,-t wall 10 and the side walls 20 at a predetermined value even after the angle product has been removed frorp. an iniection molding die for cooling or hardening.

The groove 30 is formed into a U-shaped section so as to extend along each edge portion corner portion R of the channel-shaped product E.

With respect to the dimensions of the groove preferable to determine the depth d of the groove to 60% of the wall thickness t of the bottom or in cross K at the 30, it is to be 30 side wall. 20 or 10. Similarly, it is preferable to determine tha width e of the groove to be 30 to 60% of the wall thickness ol the bottom or side wall 20 or 10. is hn-cau.- when the deoth d and the width e of the 30 is, t- h a 30:1_ cl.' the wall thickness t, 4 - POOR QUALITY 11 11 X effectively cool and harden the of -1 1: c.

L more rapidly than the boLtom wall 3,0 and the valls 20z' s,--) that it is impossible to u.,-iiforril, cool th- even at the corner portions of the product- E.FLr'k--her, i..,heri the deDth and the width e of the groove 30 exceeds 60% of the wall thickness tl, there exists another problem in that the strength of the product may be reduced.

In the injection molded angle product of the present invention, since grooves are formed along and in the vicinity of the inner edge portions of the product, the strength of the product will be decreased. Therefore, it is preferable to form a plurality of reinforcing ribs 40 at regular intervals across each groove 30 so as to extend between the bottom wall 10 and the side wall 20 as shown in drawinas.

,s described above, in the injection molded products of the)resent invention, since grooves are fori-ned alon-9 inner edge portions at- which two wall surfaces are in contact- with each other, it is possible to mo.-e ra,,-)idly coe,' o- harden the of the grooves or the ccri-i-2r portions of the angle product to prevent contraction forctz. from being generated at the corner portions bet,;ee.n two wall portions. Therefore, it is possible to securely prevent angles subtended by two walls of an angle product r from being changed after the product has been removed from an injection molding die for cooling or hardening.

POOR QUALITY

Claims

I'!1AT IS CLAIMED IS:

1. Tn an injection molded angle pro.-'-uc,, wit 11 - h c-,.

least two walls the imorovement wherein a 1 is -Lornice", along and in the vicinity of a corner portion between the two walls.

2. The injection molded angle product of claim l., wherell.. said groove is formed along one inner edge portion i-)ets.;een 10 said two walls.

3. The injection molded angle product of claim 2, said groove is formed into a U-shape in cross section.

4. The injection molded angle product of width of said U-shaped groove is 30 to of a wA'Ll thickness of the angle product.

5. The injection molded angle product o-,"' 3, of said U-shaped croove is 30 to a thickness of the angle product.

6. The injection molded angle product of clair. 1, wherein a plurality of reinforcing ribs are furthe- intervals across the groove so as to connect the two wall's.

6 h 1 1 e 1 35

7. An injection moulded product having at least two walls with an angle therebetween, characterised in that the angle is substantially the same as the corresponding angle in the die in which the product was moulded and characterised in that the product comprises a continuous or discontinuous groove formed in the vicinity of and along the length of the corner portion between the at least two walls.

8. A method of manufacturing an injection moulded product, having at least two walls with an angle therebetween, which method comprises injection moulding the product in a die, removing the product from the die and allowing the product to cool and/or harden, wherein the angle between the at least two walls is substantially the same before and after the product is cooled and/or hardened, a continuous or discontinuous groove being formed in the vicinity of and along the length of the corner portion between the at least two walls before the product is cooled and/or hardened.

9. An injection moulded product substantially as hereinbefore described with reference to, and as shown in, Figures 4, 5(A) and 5(B) of the accompanying drawings.

10. A method of manufacturing an injection moulded product substantially as hereinbefore described.

11. Any novel feature or combination of features disclosed herein.

- -7 - Published 1988 at The Patent Office. State House. 6671 High Holborn. London WC1R 4TP Further copies may be obtained from The Patent office, n_- -------- VAnt BR5 3RD Printed by Multiplex teebiiiques ltd. St Maiy Cray, Kent. Con 1187.