WO2002034494A1

WO2002034494A1 - Method for moulding a tool handle

Info

Publication number: WO2002034494A1
Application number: PCT/DK2001/000663
Authority: WO
Inventors: Poul Toft
Original assignee: Vikan A/S
Priority date: 2000-10-24
Filing date: 2001-10-11
Publication date: 2002-05-02
Also published as: AU2001295438A1

Abstract

Method for the manufacture of a handle for tools comprising the moulding of a hollow first tube in plastic material, said moulding taking place in a mould, and where in the mould there is placed a core, said core forming the cavity in the first tube, and where the core is hollow and comprises a valve in the one end, where the mould comprises two jaws/mould inserts placed on each side of the longitudinal axis of the tube, said jaws/mould inserts providing a through-going opening for the provision of a suspension part for the handle, the end surfaces of said jaws/mould inserts abutting against parts of the core during injection of plastic material, and where the core is moved a first distance in the direction away from the suspension coaxially with the longitudinal axis of the tube during simultaneous injection of the melted plastic material. There is hereby achieved a handle which has a surface and connection with the tool part and the suspension part which is configured in such a manner that the possibility of bacterial accumulations is minimised, and so that the tool may afford good possibilities for subsequent cleaning.

Description

METHOD FOR MOULDING A TOOL HANDLE

The invention concerns a method for the manufacture of a handle for tools comprising the moulding of a hollow first tube in plastic, said moulding taking place in a mould, and where a core is placed in the mould, said core forming the cavity in the first tube. The invention also concerns a handle for tools, for example squeegees, shovels, mops etc., said handle comprising a moulded, hollow first tube of plastic, and where the first tube surrounds a second tube placed in the cavity of the first tube with a part of said second tube lying outside the first tube. Finally, the invention concerns use of the method.

In connection with the use of tools, especially within the foodstuffs industry, there are very high demands concerning the hygienic characteristics of the tools employed, which for example can be mops, squeegees and shovels of various types. The authorities thus place very high demands concerning the possibilities for cleaning of the tools, and with regard to the risk of bacterial growth being minimised as much as possible.

Therefore, it is desirable to have a handle which has a surface and connection to the tool part and suspension part which is configured in such a manner that the possibility of the accumulation of bacteria is minimised, and also that the tool can offer good possibilities for subsequent cleaning. At the same time, the handle should be as light as possible, and for this reason it is important that this is hollow, which means that the moulding of a solid handle will thus be unusable for the purpose.

The object of the present invention is thus partly to provide a method for the manufacture of such a product, and partly the product itself, and which has the relevant possibilities, inasmuch as the handle which shall thus be pro- vided is very robust and tolerates great loads due to the possibility of placing a metal tube or fibre-reinforced plastic tube in the surrounding plastic handle, at the same time that the inherent weight is minimal. The plastic handle itself is moulded in such a manner that the risk of bacterial accumulations is minimised, in that the handle and the suspension part are moulded in one piece, whereby the risk of bacterial accumulations is minimised. Here is must be mentioned that it is known to mould tubes, but the possibility of moulding a hollow tube where the suspension part constitutes an integral part of said tube has never hitherto been seen.

This object is achieved with a method of the kind disclosed in the preamble, and where the core is hollow and comprises a valve in the one end, where the mould comprises two jaws/mould inserts on each side of the longitudinal axis of the tube, said jaws/mould inserts creating a through-going opening for the provision of a suspension part for the handle, the end surfaces of said jaws/mould inserts abutting against parts of the core during the injection of plastic material, and where the core is moved a first distance in the direction away from the suspension coaxially with the longitudinal axis of the tube during simultaneous injection of the melted plastic material.

The handle itself is thus characterised by the actual suspension part constituting an integral part of the handle, so that a complete unit is achieved without assembly joints. The method itself is unique, in that a moulding of the handle is effected in one piece. The moulding thus takes place in a closed mould in which a core is placed, said core having a through-going channel which ends in an upper cone valve. A fluid plastic material is now injected into the one end, corresponding to the area where the cone valve is placed, and in other respects where the suspension part itself will be disposed later. The plastic material is distributed between the outer surface of the core and the inside of the mould in the formation of a hollow tube. The mould also comprises two jaws/mould inserts, each in a mould part and lying at right-angles to the longitudinal axis of the tube, and upon opening of the mould said jaws/mould inserts are displaced laterally together with each mould half part, and said jaws/mould inserts will be lying under the first portion of fluid plastic material with parts of the end surfaces of the jaw/mould insert towards each other. The jaws/mould inserts will have contact against the core with parts of their end surfaces so that the core does not topple during the moulding. When a certain amount of plastic material has been injected, there subsequently occurs a withdrawal of the core during continued injection, corresponding to 3-4 mm, and since a part of the plastic material will already have solidified, this will ensure that the core does not topple.

The injection of the plastic material takes place continuously, and con- eludes when the moulding of the suspension part is finished. As a consequence of the placing of the jaws/mould inserts during the first part of the injection of melted plastic material, the core thus does not topple, and subsequently, when the core is drawn back, it is ensured that neither during this part of the process, i.e. during injection of the additional plastic, is the core able to topple, because parts of the tube itself are now solidified. By this method, there is thus ensured not only the moulding of a hollow tube, but also the production of an integrated suspension part.

By providing a method according to the invention and as disclosed in claim 2, the possibility is achieved of being able to remove the finished item, in that the air injected into the inside of the core at approx. 20 bar leaves the core through the valve and migrates along the outer side of the core and the inner surface of the tube where it serves as an air cushion.

By providing a method according to the invention and as disclosed in claim

3, it is achieved that the suspension part is formed in an expedient manner. By providing a method according to the invention and as disclosed in claims 4 and 5, it is achieved that the moulding of both the handle and the suspension part is made possible in one moulding operation, and that an after- filling of the area at the jaws/mould inserts takes place, so that this does not constitute a weak link or possibly does not receive a complete filling-up during the first injection shot.

By providing a method according to the invention and as disclosed in claim 6, a moulding without transitions is achieved.

By providing a method according to the invention and as disclosed in claim

7, it is achieved that the connection area between inner and outer tube is made 100% resistant and repellent to bacterial in-growth.

By providing a method according to the invention and as disclosed in claim

8, it is achieved that the metal tube or the fibre-reinforced plastic tube which is placed inside the plastic tube assumes a firm connection with this. The second tube can possibly be pressed into the first tube while it is still hot, after which the outer tube contracts during heat dissipation, whereby a handle is achieved where the risk of bacterial in-growth is minimised.

The invention also concerns a handle as disclosed in the preamble, and where the handle comprises a suspension part which is moulded together with the first tube, and where the second end part of the first tube opposite the suspension part is slightly conical and surrounds the second tube by press-fitting/shrinking. There is hereby achieved a tool handle on which the tool part can be mounted without risk of the earlier mentioned bacteria accumulations. The invention also concerns use of the method according to claims 1-8, and for the manufacture of a handle according to claims 9-11.

The invention will now be explained in more detail with reference to the drawing, where

fig. 1 shows a handle according to the invention,

fig. 2 shows the handle shown in fig. 1 , where a metal tube is mounted inside the plastic material, and also shows sections of this,

fig. 3 shows a section corresponding to section Ill-Ill in fig. 2, and

fig. 4 shows a detail view seen in section through the suspension part corresponding to section IV-IV in fig. 1.

Fig. 1 shows a handle 1 produced according to the invention, comprising a hollow, substantially cylindrical first tube 2 made of plastic material. On the first tube 2 and integrated herewith there are ribs 11 which are formed as oval elements which constitute an integrated part of the surface of the first tube. The first tube 2 is produced in a thermoplastic moulding material, preferably polypropylene, and where in its basic form this is moulded substantially cylindrical. In the one end part of the handle, called the second end area, the end of the first tube converges towards the clearing at an angle of approx. 84° in the formation of a conical part 10, so that the outer diameter of the first tube typically lies at 34 mm, while the smallest diameter of the conical end is approximately 30 mm, and is finally concluded with a chamfer of 45°. With this conical shape, a tight connection of the first tube against the inner second tube 8 is ensured, which will otherwise be described later. In the opposite end of the first tube, called the one end 4 of the first tube, a suspension part 3 is provided. This suspension part 3 constitutes an integrated part of the whole of the first tube, in that in connection with the moulding it is moulded in connection with the first tube. The suspension part 3 is formed with an oval and through-going opening 5, where the oval has a larger breadth at the one end than the second end nearest to the tube. With this suspension there is thus provided an eye surrounded by a solid, U- shaped tube part, and with the closure part towards the tube comprising two inclined surfaces 6.

As will appear from fig. 4, the area between the suspension part and the first tube comprises two inclined surfaces 6 which converge towards the cavity 5, and between them they form an angle of 80-100°, preferably around 90°. In the first tube 2 there is placed a second tube 8, preferably a hollow tube of aluminium, which has the advantage that it serves as a stiffener while at the same time being relatively light. The second tube 8 can also be produced in fibre-reinforced plastic material, and it could also be a compact cylindrical rod.

The second tube 8 thus lies axially parallel with the first tube 2, and is pressed into the first tube 2 when this has just been taken out of the mould, during which it has a temperature of between 80 and 100°. During the sub- sequent cooling, a shrinking of the first tube around the second tube will occur.

In connection with the pressing of the second tube into the first tube, a part

9 of the second tube will protrude out of the first tube, so that the conical part 10 will ensure a completely tight connection between the first and second tube during the shrinking which occurs with the cooling of the first tube.

The actual moulding of the handle takes place by the first tube 2 being moulded in e.g. polypropylene in a closed mould, this mould comprising a core with a bore which forms a channel from the one end surface to the second end surface, and where at the one end this bore ends in a valve, preferably a conical valve, which is influenced by a spring. This valve lies in the end nearest to the suspension part 3. The cavity in the first tube is thus brought about by the core.

The plastic moulding material is now injected under high pressure, preferably around 1200 bar, in the area where the centre of the suspension part coincides with the centre axis of the tube. The mould, which comprises two mould half parts, here comprises a pair of jaws/mould inserts associated with each mould part, and which lie at right-angles to the centre axis of the tube, said jaws/mould inserts coming together in an area corresponding to the edge 7 defined by the inclined surfaces 6, said edge 7 lying in the centre plane of the tube and thus forming the cavity/the opening during the moulding. The opening part of the suspension part is thus a result of the jaws/mould inserts which fill out that part which later forms the opening. The two half parts, which form the finished suspension hole, are fixed inserts in the mould parts, so that when the mould is closed, the two parts come together in the centre and hereby form the hole.

At the start of the injection, the 25 mm-long core moves up and is supported against the two parts which form the hole in the handle, otherwise this core would topple over to the one side due to the injection pressure. During the injection, the plastic mass migrates down along the side, and at a time when it is ensured that the plastic mass surrounds the whole of the internal core, and for a suitable length, the core is withdrawn to form the "bottom" in the cavity. The very necessary support of the core, which is achieved by letting this move against the handle cavity inserts, is "taken over" by the plastic mass when this has sufficient volume, and the core can be drawn back the 4 mm, whereby the inclined surfaces 6 are formed. Hereafter, air/gas at a pressure of around 25 bar is injected into the inner cavity of the core corresponding to the opposite end of the first tube, while at the same time the tool opens for around 1 mm in all.

The conical valve is opened by a spring influence as a result of that pressure which is now generated. The air leaves the core at the same time that, as mentioned, a slight opening of the mould of around 0.4 mm occurs between the inner surface of the mould and the outer surface of the first tube, whereby the air, which is blown through the inside of the core, will migrate along the surface of the core and the inner surface of the first tube and form an air cushion, after which the mould is opened completely, and the finished product can be taken out without any risk of a collapsing of the product taking place.

The reason why the mould is opened only very slightly is that the item is still very hot, and there is a great risk of a balloon being blown out at the top before the cooling air is established, and this slight opening ensures against this blowing out. As soon as the cooling air is in function all the way around and all the way down, the mould is opened completely and the item is blown off at relatively high speed.

The product will typically have a temperature of approx. 80-100°, and as mentioned earlier the second tube is placed in the cavity in which the core was placed earlier. During the subsequent cooling, the plastic material will shrink, whereby the second tube will come to sit 100% and positively firm inside the first tube 2. A complete closing is ensured precisely by the open end of the first tube ending in a conical manner. The handle is now ready to be used for the final manufacture of this tool.

It should also be mentioned that the advantage of the ribs is that the process can be controlled, and so that the correct distance is achieved during the opening of the mould. The height of the ribs will typically be around 1.8 mm.

Claims

1. Method for the manufacture of a handle for tools comprising the moulding of a hollow first tube in plastic material, said moulding taking place in a mould, and where a core is placed in the mould, said core forming the cavity in the first tube, characterised in that the core is hollow and comprises a valve in the one end, that the mould comprises two jaws/mould inserts on each side of the longitudinal axis of the tube, said jaws/mould inserts forming a through-going opening for the provision of a suspension part for the handle, the end surfaces of said jaws/mould inserts abutting against parts of the core during the injection of the plastic material, and in that the core is moved a first distance in the direction away from the suspension coaxially with the longitudinal axis of the tube during simultaneous injection of melted plastic material.

2. Method according to claim 1, characterised in that the mould is opened to provide an essentially small gap between the inner surfaces of the mould and the outer surfaces of the tube, that air/gas is injected into the cavity of the core, and that the valve opens at a given pressure by injection of air/gas into the cavity of the core.

3. Method according to claim 1 or 2, c h a racte ri s ed in that the opening is defined by a U-shaped suspension part moulded together with the tube and by the moulded closure of the end of the tube in the forming of the suspension part.

4. Method according to any of the foregoing claims, characterised in that with the movement of the core a first distance, the jaws/mould inserts relinquish their contact against the core.

5. Method according to any of the foregoing claims, characterised in that the lower limit of the opening towards the tube is moulded as two inclined surfaces, said surfaces diverging away from the opening and merging together in an edge which coincides substantially with the centre plane of the tube.

6. Method according to claim 3 or 4 or 5, characterised in that the plastic material is injected in the area at the suspension, said injection being a continuous injection of the melted plastic material during the whole of the moulding process.

7. Method according to any of the foregoing claims, characterised in that at the second end area which lies opposite the suspension, the first tube is formed in a slightly conical manner with walls which converge to- wards the clearance in the tube.

8. Method according to any of the foregoing claims, characterised in that the mould is opened for the removal of the moulded item, and that a second tube is thereafter pressed into the inner cavity of the item, prefer- ably for most of the length of the first tube, and that a part of said second tube lies outside the first tube.

9. Handle for tools, for example squeegees, shovels, mops etc., said handle comprising a moulded, hollow first tube of plastic, and said first tube surrounding a second tube placed in the cavity of said first tube, with a part of the second tube lying outside the first tube, characterised in that the handle comprises a suspension part which is moulded together with the first tube, and that the second end part of the first tube opposite the suspension part is slightly conical and surrounds the second tube by a press- fitting/shrinking.

10. Handle according to claim 9, characterised in that the suspension part comprises a through-going opening at right-angles to the longitudinal axis of the tube, and which concludes nearest the tube with two inclined surfaces which diverge away from the opening.

11. Handle according to claim 10, characterised in that the angle measured between the surfaces and facing towards the tube lies in the interval 80-100°.

12. Use of the method according to claims 1-8 for the manufacture of a handle according to claims 9-11.