GB2324266A

GB2324266A - A mould with ejector for the moulded article

Info

Publication number: GB2324266A
Application number: GB9707077A
Authority: GB
Inventors: R R J Daniels
Original assignee: Guy Raymond Engineering Co Ltd
Current assignee: Guy Raymond Engineering Co Ltd
Priority date: 1997-04-08
Filing date: 1997-04-08
Publication date: 1998-10-21
Anticipated expiration: 2017-04-08
Also published as: GB2324266B; GB9707077D0

Abstract

A mould is disclosed for moulding a pedestal base for a chair or other furniture item comprising a plurality of arms 12 extending radially outwardly from a hub 14, each arm comprising a channel section portion 22 within which a lattice arrangement of ribs 28, 30 is disposed, ribs of each lattice arrangement being interconnected at at least some lattice junctions 32 by respective tubular members 34. The mould comprises a female mould part for defining the side and upper extemal surfaces of the base and a male mould part having cores for defining internal surfaces of the base including the surfaces of the ribs 28, 30 and tubular members 34. The male mould part is provided with ejection sleeves which are slideable over cores of the mould and which define the interior of the tubular members during moulding, to extended positions for pushing a moulding off the cores once the female and male mould parts have been separated.

Description

Moulding articles including lattice arrangement of ribs This invention relates to the moulding of articles which include a lattice arrangement of ribs.

Particularly, but not exclusively, the invention relates to the moulding of articles in which such a lattice arrangement is disposed within a channel section portion to strengthen the same.

An example of such an article is a pedestal base for a chair (or other item of furniture) which base comprises a plurality of arms (typically five) extending radially outwardly from a hub, each arm comprising a channel section portion within which a lattice arrangement of ribs is disposed. When fitted to a chair the channel section port ions are inverted so that the bottoms of these portions are uppermost and the ribs are hidden from view.

During injection moulding of such pedestal bases, after the mould is opened following injection thereinto of the material which forms the base typically a glass filled polyamide - and cooling of the material, the base is ejected from the mould cores which define the cavities between the ribs.

Two ejection arrangements are presently known for ejecting the moulded base from the mould cores. In one of these arrangements ejection pins extend through the cores to engage the inside of the bottom of the channel section portion. Actuation of the ejection pins so that they extend from the cores pushes the moulding off the cores. A disadvantage of this arrangement is that the ejection pins act on the bottom of the channel section of the base arms and if the moulding has not cooled sufficiently prior to ejection the bottom of the channel section may be deformed by the ejection process thereby spoiling the visual appearance of the base.

In the other ejection arrangement the above disadvantage is avoided, and therefore cooling and consequentially moulding times can be reduced, by having the ejection pins engage the edges of the ribs and possibly the free edges of the side walls of the channel section portion remote from the bottom of the channel section. That is the trailing edges in the ejection direction. However, in this case because the ribs and side walls are relatively thin, the diameter of the ejection pins which cannot be greater than the thickness of the ribs and side walls on which they act has to be small compared to that of the pins used in the first arrangement discussed above. Accordingly a significantly greater number of ejection pins are required in order to provide the same ejection force.

Due to the small diameter and large number of ejection pins required the mould is expensive.

Broadly, the invention concerns a modification of the second ejection arrangement since it utilizes ejection members which engage trailing edges of the lattice arrangement in the ejection direction.

According to the invention these ejection members comprise sleeves which slide over cores which define the interior of tubular members, or bosses, provided at at least some of the junctions of the lattice arrangement.

In one aspect, the invention provides a mould for a moulding comprising a lattice arrangement of ribs wherein the ribs are interconnected at at least some lattice junctions by respective tubular members, said mould comprising first cores corresponding to the spaces to be formed between adjacent ribs, second cores corresponding to the spaces to be formed internally of said tubular members, and ejection sleeves for defining at least partly ends of said tubular members during moulding and slidable over said second cores for pushing a moulding off said first and second cores.

Such a mould may be used for a moulding in which said lattice arrangement is disposed within a channel section portion, for example for a moulding of a pedestal base arm, and in this case the mould preferably has a female part for defining the exterior of said channel section portion and said ejection sleeves are arranged for at least partly defining the ends of the tubular members remote from the bottom of the channel section portion.

In another aspect the invention provides a method of moulding a lattice arrangement of ribs wherein the ribs are interconnected at at least some lattice junctions by respective tubular members, including ejecting the moulding from first cores forming the spaces between adjacent ribs and second cores forming the spaces internally of said tubular members using ejection sleeves which at least partly define ends of said tubular members during moulding, said sleeves being slid over said second cores to push the moulding off said first and second cores.

Such a method may be used for a moulding in which the lattice arrangement is disposed in a channel section portion and in this case the ejection sleeves at least partly define the ends of said tubular members remote from the bottom of the channel section portion.

The invention extends to an article when moulded in a mould as defined in the last but three or last but two paragraphs or by a method as defined in the last but one or the last preceding paragraph.

In the preferred embodiment of the invention described hereinafter the article moulded utilizing ejection sleeves which are slidably moveable over cores which form the interior of tubular members located at at least some lattice junctions of a lattice arrangement of ribs is a pedestal base having a plurality of arms, each of which is provided with such a lattice arrangement disposed within a respective channel section portion.

The preferred embodiment of a mould comprises a mould for moulding a pedestal base for a chair or other furniture item comprising a plurality of arms extending radially outwardly from a hub, each arm comprising a channel section portion within which a lattice arrangement of ribs is disposed, ribs of each lattice arrangement being interconnected at at least some lattice junctions by respective tubular members, said mould comprising a female mould part for defining the side and upper external surfaces of the base and a male mould part having cores for defining internal surfaces of the base including the surfaces of said ribs and tubular members, said male mould part being provided with ejection sleeves slidable over cores of the mould which define the interior of said tubular members from retracted positions within the male mould part for at least partly defining the ends of the tubular members during moulding to extended positions for pushing a moulding off the cores once the female and male mould parts have been separated.

The invention also includes an injection moulded pedestal base for a chair or other furniture item comprising a plurality of arms extending radially outwardly from a hub, each arm comprising a channel section portion within which a lattice arrangement of ribs is disposed, ribs of each lattice arrangement being interconnected at at least some lattice junctions by respective tubular members.

In order that the invention may be well understood the preferred embodiment thereof referred to above, which is given by way of example only, will not be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a pedestal base for a chair; Figure 2 is a bottom plan view of the base; Figure 3 is an enlarged view corresponding to part of Figure 2; Figure 4 is a section along the line IV-IV in Figure 3; and Figure 5 is a view similar to Figure 3 showing a modification to the preferred embodiment.

The illustrated pedestal base for a chair is referenced 10 and comprises a plurality of arms 12 extending radially outwardly from a hub 14. The hub 14 is provided with a through bore 16 for accommodating a column of a chair (not shown). The radially outer end 18 of each arm 12, of which there are five in the illustrate base, is provided with a bore 20 for receiving a mounting spindle of a castor (not shown).

Each arm comprises a channel section portion 22 having a bottom 24 and side walls 26. Within the channel section portion 22 a lattice arrangement of ribs 28, 30 is disposed for strengthening the channel section portion. In the lattice arrangement the ribs 28, 30 are interconnected at lattice junctions 32 along the centre line of the arm by tubular members, or bosses, 34.

Each rib 28 extends between a tubular member 34 and a side wall 26 and each rib 30 extends along the arm centre line. The ribs 28, 30 extend from the bottom of the channel section portion to which they are joined coextensively with the side walls 26 as shown for ribs 28 in Figure 4.

The base 10 is injection moulded as a one piece article from a suitable injection mouldable material.

In the preferred embodiment this material is a glass filled polyamide.

The mould (not shown) for moulding the base 10 comprises a female mould part for defining the side and upper external surfaces of the base, including the outer surfaces of the bottom 24 and side walls 26 of the channel section portion 22, and a male mould part having cores for defining internal surfaces of the base including the surfaces of the ribs 28, 30 and the tubular members 34. The male mould part is provided with ejection sleeves which are slidable over cores of the male mould part which define the interior of the tubular member. In the embodiment these cores and the ejection sleeves are cylindrical. However, they could have cross-sections which are non-circular. The ejection sleeves are slidable for retracted positions within the male mould part where they at least partly, and preferably completely, define the ends of the tubular members 34 during moulding, to extended positions for pushing the moulded base off the male mould part cores once the female and male mould parts have been separated. In the embodiment the wall thickness of the tubular members 34 is substantially the same as the wall thickness of the ejection sleeves.

It will be appreciated that the male mould part comprises cores, hereinafter referred to as first cores, corresponding to the spaces to be formed between adjacent ribs 28, 30 and other cores, hereinafter referred to as second cores, corresponding to the spaces to be formed internally of the tubular members 34 and the ejection sleeves which at least partly define the ends of the tubular members during moulding slide over the second cores to push the moulding off the first and second cores.

In the embodiment, the bore 20 at the outer end of each arm is defined by a tubular member or boss 36.

An ejection sleeve slidable over the core which defines the bore 20 during moulding is provided and functions in the same way as the previously described ejection sleeves. Thus, in a retracted position within the male mould part, this ejection sleeve at least partly defines the end of the tubular member 36 during moulding and once the male and female mould parts have been opened this ejection sleeve is moved to an extended position in synchronism with such movement of the ejection sleeves associated with the tubular members 34. As will be appreciated the ejection sleeves act along the length of each arm at spaced intervals.

The ejection sleeves do not act on the bottom 24 of the channel section portion 22 as is the case with the first known ejection arrangement discussed above and accordingly the disadvantages associated with that arrangement do not arise. However, each sleeve has a considerably greater cross-section than the cross section possible for the ejection pins of the second known ejection arrangement discussed above and accordingly to the number of ejection sleeves required to provide the same ejection force is significantly less than the number of pins need in the second ejection arrangement. Also it will be appreciated that manufacture of a male mould part having the ejection sleeves of the embodiment is easier than manufacture of a male mould part having the known ejection pin arrangement not only because of the reduction of the number of ejection members required but also because manufacturing tolerances need not be so fine.

In the preferred embodiment the ribs 30 which extend along the arm centre line do not extend through the tubular members 34. However, it is envisaged that in order to improve the structural strength of the arms they may do so as indicated in Figure 5. In this case the cores defining spaces internally of the tubular members are slotted in the region of the mould cavity to interconnect the ribs 30 on each side of each tubular member.

It will also be appreciated that alternatively or additionally one or both of the diametrically opposite pairs of ribs 28 at each tubular member may extend through that tubular member, the core members defining the spaces internally of the tubular members being appropriately slotted.

It is to be understood that whilst the ejection arrangement of the preferred embodiment, in which the lattice arrangement is disposed in a channel section portion, is particularly applicable to that embodiment, it may be utilised in the moulding of lattice arrangements of ribs which are not disposed in channel section portions.

Claims

CLAIMS:

1. A mould for a moulding comprising a lattice arrangement of ribs wherein the ribs are interconnected at at least some lattice junctions by respective tubular members, said mould comprising first cores corresponding to the spaces to be formed between adjacent ribs, second cores corresponding to the spaces to be formed internally of said tubular members, and ejection sleeves for at least partly defining ends of said tubular members during moulding and slidable over said second cores for pushing a moulding off said first and second cores.

2. A mould as claimed in claim 1 for a moulding in which said lattice arrangement is disposed within a channel section portion, said mould having a female part for defining the exterior of said channel section portion and said ejection sleeves being arranged for at least partly defining the ends of said tubular members remote from the bottom of the channel section portion.

3. A method of moulding a lattice arrangement of ribs wherein the ribs are interconnected at at least some lattice junctions by respective tubular members, including ejecting the moulding from first cores forming the spaces between adjacent ribs and second cores forming the spaces internally of said tubular members using ejection sleeves which at least partly define ends of said tubular members during moulding, said sleeves being slid over said second cores to push the moulding off said first and second cores.

4. A method as claimed in claim 3 wherein said lattice arrangement is disposed in a channel section portion and wherein said ejection sleeves at least partly define the ends of said tubular members remote from the bottom of the channel section portion.

5. A mould as claimed in claim 1 or 2 or a method as claimed in claim 3 or 4 wherein said second cores and said ejection sleeves are substantially cylindrical.

6. A mould as claimed in claim 1, 2 or 5 or a method as claimed in claim 3, 4 or 5, wherein the wall thickness of said tubular members is substantially the same as the wall thickness of said ejection sleeves.

7. An article when moulded in a mould as claimed in claim 1, 2, 5 or 6 or by a method as claimed in claim 3, 4, 5 or 6.

8. An article as claimed in claim 7, wherein said article is a pedestal base having a plurality of arms each of which is provided with a lattice arrangement of ribs disposed within a respective channel section portion.

9. A mould for moulding a pedestal base for a chair or other furniture item comprising a plurality of arms extending radially outwardly from a hub, each arm comprising a channel section portion within which a lattice arrangement of ribs is disposed, ribs of each lattice arrangement being interconnected at at least some lattice junctions by respective tubular members, said mould comprising a female mould part for defining the side and upper external surfaces of the base and a male mould part having cores for defining internal surfaces of the base including the surfaces of said ribs and tubular members, said male mould part being provided with ejection sleeves slidable over cores of the mould which define the interior of said tubular members from retracted positions within the male mould part for at least partly defining the ends of the tubular members during moulding to extended positions for pushing a moulding off the cores once the female and male mould parts have been separated.

10. An injection moulded pedestal base for a chair or other furniture item comprising a plurality of arms extending radially outwardly from a hub, each arm comprising a channel section portion within which a lattice arrangement of ribs is disposed, ribs of each lattice arrangement being interconnected at at least some lattice junctions by respective tubular members.

11. A mould, method or moulding substantially as hereinbefore described with reference to the accompanying drawings.