WO2004106028A1

WO2004106028A1 - Process for giving a rod its final shape

Info

Publication number: WO2004106028A1
Application number: PCT/EP2004/005527
Authority: WO
Inventors: Alfonso Branca
Original assignee: Top Glass S.P.A.
Priority date: 2003-05-28
Filing date: 2004-05-21
Publication date: 2004-12-09
Also published as: ITMI20031066A1; ITMI20031066A0

Abstract

The process for giving a rod (18) its final shape through moulding has a step in which an expanding element (20) is introduced under pressure along at least one portion of the axis of the rod (18) positioned or pushed in the impression (9, 10) of the mould (1) to cause a substantially radial expansion of at least one axial portion of the rod (18) suitable for shaping it according to the impression of the mould.

Description

PROCESS FOR GIVING A ROD ITS FINAL SHAPE

DESCRIPTION

The present invention refers to a process for giving a rod its final shape through moulding, preferably but not exclusively for realising bolts or similar connection elements .

As is known, bolts and similar connection elements are generally made from metal through machine processing, hot or cold moulding and melting.

Some properties of metals are, however, disadvantageous in certain applications, for example the high density of some metals can add a considerable weight to a structure_/ the susceptibility to corrosion of some metals can put the resistance of a structure at risk, or the high electrical conductivity that can cause phenomena of interference of a structure with electronic structures arranged nearby.

For this reason, to realise bolts or similar it has been thought of to use plastic materials, and preferably composite materials reinforced with continuous longitudinal fibre, with which properties of lightness and mechanical resistance can be achieved.

Articles in composite material are realised from a rod obtained through a pultrusion process.

For the finishing of a bolt, the rod in composite material is generally subjected to machine processing, a thing that as well as involving a certain waste of material can cause the cutting of some longitudinal fibres and therefore the weakening of the structure of the resulting product.

For this reason the method of moulding a round bar or a rod of thermoplastic composite material made from longitudinal fibres has recently been adopted, pushing it into a mould with a substantial pressure, after having heated it up to the point in which it is mouldable.

The round bar must have a greater length than the desired length of the bolt, since during forming the rod shortens deforming by compression to fill the head and the threading of the impression of the bolt in the mould.

One of the biggest drawbacks of this method is that the longitudinal fibres of the composite material tend to bulge and flex during the forming of the bolt causing a weakening of the mechanical properties of the end product, since they substantially depend upon the orientation of the reinforcement fibres.

Last but not least, it should be noted that conventional bolts, which can differ for even minimal structural details and can have minimal differences even only in diameter, are sometimes easily confused.

The rushed and unsuitable choice of a bolt can affect the quality of the mechanical coupling realised by it and, moreover, a considered choice requires patience and time which may not always be available.

The technical task proposed of the present invention is, therefore, that of providing a method for giving a rod its final shape through moulding that allows the aforementioned technical drawbacks of the prior art to be eliminated.

In this technical task a purpose of the invention is that of realising a method for giving a rod its final shape through moulding that does not determine the shortening of the rod, so that, should a composite material be used for the rod, the orientation of the reinforcing fibres is not substantially changed and the characteristics of mechanical resistance of the rod are not substantially impaired.

Another purpose of the invention is that of realising a method for giving a rod its final shape through moulding that, should a composite material be used for the rod, completely preserves the integrity of the reinforcing fibres.

Yet another purpose is that of realising a method for giving a rod its final shape through moulding that does not determine waste of material, and that is simple and cost- effective .

The last but not least purpose of the present finding is that of providing a method for giving a rod its final shape through moulding that creates an end product that is easily recognisable even by people with no great ability and expertise .

The technical task, as well as these and other purposes, according to the present invention are accomplished by realising a process for giving a rod its final shape through moulding characterised in that an expanding element is introduced under pressure along at least one portion of the axis of said rod positioned or pushed in the impression of the mould to cause a substantially radial expansion of at least one axial portion of said rod suitable for shaping it according to said impression of said mould.

Preferably, the rod consists of composite material with thermoplastic or thermo-setting, respectively, resinous matrix not yet completely polymerised.

In this case the process also comprises a heat treatment step suitable for making the thermoplastic matrix of the rod mouldable or for completing the polymerisation of the thermo- setting matrix of the rod, respectively.

Other characteristics of the present invention are defined, furthermore, in the subsequent claims.

Further characteristics and advantages of the invention shall become clearer from the description of a preferred but not exclusive embodiment of the moulding process of a bolt according to the finding, illustrated for indicating and not limiting purposes in the attached drawings, in which: figure 1 shows a perspective view of the main components of a mould according to the invention for giving a rod or ound bar its end shape as a bolt; figure 2 shows a perspective view of the mould of figure

1 open after the moulding of the bolt; figure 3 shows a perspective view of the mould of figure

1 closed and containing a rod to be moulded; and figure 4 shows a bolt produced by the mould of figure 1.

With reference to the quoted figures, a mould 1 for a bolt

2 is shown, suitable for the moulding of a rod preferably of composite material having a resinous matrix and a continuous longitudinal reinforcing fibre, i.e. parallel to the axis of the rod 18.

The mould 1 has a block 3 and a counter block 4 , respectively, substantially parallelepiped in shape, the block 3 in turn having a face 5 fitting onto a counter face 6 of the counter block 4 for the closing of the mould 1.

The face 5 of the block 3 and the counter face 6 of the counter block 4 have an abutment system to align the block 3 with the counter block 4 in the act of closing the mould 1, formed for example by matching ridges 7 and grooves 8.

The face 5 of the block 3 and the counter face 6 of the counter block 4 have semi-impressions 9 and 10 of the bolt 2, also fitting together exactly upon closure of the mould 1 to define the overall impression 11 of the bolt 2.

Along the axis of the impression 11 and on the opposite side of the impression 11 an access channel 12 to the impression 11 and a discharge channel 13 from the impression 11 extend in the mould 1.

Like .for the impression 11, the access channel 12 and the discharge channel 13, respectively, also have a semi-part 14 and 15 respectively, formed in the face 5 of the block 3 and a semi-part 16 and 17 respectively, formed in the counter face 6 of the counter block 4.

The mould 1 preferably carries heating means (not shown) , for example one or more electrical resistances, suitable for taking the round bar 18 to a temperature in which it becomes mouldable .

The mould 1 also has a thruster 19 mobile along the access channel 12 to introduce a pin 20 in the impression 11 of the mould 1.

The thrusters 19 has a diameter substantially equal to that of the access channel 12 and of the round bar 18, whereas the pin 20 moved by it has a substantially smaller diameter. In this way the access channel 12 guides the stroke of the thrusters 19 along the axial direction of the round bar 18 to thrust the round bar in the impression 11.

The pin 20 can have a point 21, as illustrated, and a widened end 22 to form the head of the bolt 2.

The side surface of the pin 20 can be smooth or threaded, as we shall see, according to the application.

The discharge channel 13 is suitable both for discharging air when the mould 1 is operative and for receiving the point 21 of the pin 20.

In the embodiment illustrated now the thrusters 19 and the pin 20 are realised in a single piece, but even more advantageously for other applications, as we shall see, it is possible to foresee that the thrusters 19 ^' be detached from the pin 20 or able to be coupled with it with removable engagement means for example in the form of screw coupling means .

The process for realising the bolt 2 consists of pressure introducing the pin 20 along the axis of the round bar 18 to cause a substantially radial expansion of the round bar 18 suitable for shaping it according to the impression 11. In this way material coming from the axis of the round bar 18 is used to fill the head and the threading of the impression 11 of the bolt, so that the rod does not change length and the reinforcing fibres that is has are not subjected to a change in orientation.

In greater detail, the process for realising the bolt 2 consists of the following steps.

Firstly, the mould ^'1 is opened and the round bar 18 is positioned in the impression 11, whereas the pin 20 is arranged in the access channel 12, and thus completely outside of the impression 11, preferably after the closing of the mould 1.

Then the electrical resistances of the mould 1 are actuated to take the round bar 18 to a temperature in which it is mouldable.

The round bar 18 can, however, be pushed into the impression 11 even after the closing of the mould 1.

Optionally, if the mould does not possess heating means of the round bar 18, the same purpose can be achieved by previously heating the round bar 18 in any other way outside of the mould 1.

When the round bar 18 reaches the ideal temperature for moulding, suitable command means (not illustrated) actuate the thrusters 19 which in turn moves the pin 20 towards the inside of the impression 11.

The command means can give the thrusters 19 a translational or roto-translational advancing motion.

Purely translational motion is used in the case in which the side surface of the pin 20 is substantially smooth.

On the other hand, in the case in which the side surface of the pin 20 is threaded, through a roto-translational advancing movement of the pin 20 a threaded channel can be generated along the axis of the round bar 18 for the screw coupling of the bolt 2 with another element (not shown) .

At the end of the moulding the command means command the withdrawal of the thrusters 19 and consequently the extraction of the pin 20 from the recess 23 which it has formed along the axis of the bolt 2.

At this point the recess 23 of the bolt 2 can be left free or an insert (not shown) can be introduced into it .

As an example, the free recess 23 could be used to pass a cable or a tube through elements which must be connected by the bolt .

In other applications the recess 23 can also act positively in the sense of lightening the overall weight of the bolt.

The insert can advantageously consist of a material suitable for improving the characteristics of mechanical resistance of the bolt 2 or other characteristics of the bolt, and/or it can be provided in various colours each one identifying a specific characteristic of the bolt 2.

For example, the insert can be made from elastomeric material particularly suitable for the damping of vibrations, it can be made from composite material to mechanically reinforce the bolt, it can incorporate a connector to join parts of a structure, it can have at least one phosphorescent part to be easily identifiable, it can have a shaped head to distinguish, protect, decorate, etc. the head of the bolt, it can have different colourations each identifying a corresponding diameter of the bolt 2.

The insert can be applied through adhesive or by pressure or by heating the interface with the recess 23.

The pin can be inserted completely, as shown, or even partially along a portion of the axis of the rod 18, for example in the case in which the mechanical characteristics at one end of the bolt are less critical and even allow a flexing of the reinforcing fibres .

Moreover, the rod to be deformed into the bolt can consist of a composite material having fibres that extend in a direction other than the axial direction.

This can be achieved for example if the rod is realised through pultrusion by incorporating a mat of continuous threads . or strings of continuous threads, and it is advantageous in that the fibres out of axis have mechanical resistance in directions in which axial fibres can have little, for example to resist turning moments or shear stresses .

The rod 18 can also consist of a composite material with a thermo-setting resin-based matrix that is not completely polymerised (a pre-soaked composite) , taken to complete polymerisation during the heating process of the rod.

Since in the moulding process the pin 20 determines a radial expansion along the axial extension of the round bar 18, the length of the round bar 18 and consequently the orientation of the fibres in the finished product shall not be appreciably modified.

In the case in which the pin 20 is detached or removable from the thrusters 19, instead of removing the pin 20 from the recess 23 of the bolt 2, it is also possible to leave it definitively inside it as an insert, in which case the pin could, for example, advantageously consist of composite material .

The moulding process and the mould thus conceived is susceptible to numerous modifications and variants, all of which are covered by the inventive concept; moreover, all of the details can be replaced with technically equivalent elements .

In practice, although the description refers to a bolt, the present invention is equally applicable for any other type of .connection elements such as screws, rivets, etc.

In particular, the invention has an application to shape a rod with a fattened head of any shape, for example conical.

The process of the present invention can be used more generally to give a rod of composite material its end shape.

For example, the process can be used to realise the handle of a hammer, and in this case the recess formed by the pin of the mould can be used to house a support for the head of the hammer .

Finally, the expanding element can be in the form of a pin, as illustrated, preferably in the case in which the rod to be formed is full, but advantageously it can also be in the form of another expanding element, for example progressive expansion expanding element such as a pressurisable ball, when the rod has a recess suitable for housing such an expanding element.

Claims

1. Process for giving a rod its final shape through moulding characterised in that an expanding element is introduced under pressure along at least one portion of the axis of said rod positioned or pushed in the impression of the mould to cause a substantially radial expansion of at least one axial portion of said rod suitable for shaping it according to said impression of said mould.

2. Process for ^■ giving a rod its final shape through moulding according to claim 1, characterised in that a rod of composite material is used.

3. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said rod of composite material is used with a thermoplastic matrix.

4. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that heating is foreseen to make said rod of composite material with thermoplastic matrix mouldable.

5. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said rod of composite material with thermo-setting matrix is used not completely polymerised.

6. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that a heating is foreseen to complete the polymerisation of said thermo-setting matrix.

7. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said composite material has continuous reinforcing fibres parallel to the axis of said rod.

8. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said heating is carried out before or after the positioning of said rod in said mould.

9. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that the introduction of said expanding element in said rod takes place with translational or roto- translational advancing motion of said expanding element in said rod.

10. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said expanding element is left as an insert of said rod.

11. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said expanding element is withdrawn from the recess that it forms along the axis of said rod to introduce an insert in its place.

12. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said rod is full and said expanding element is a pin.

13. Process for giving a rod its final shape through moulding according to one or more of the previous claims, characterised in that said rod has a recess and said expanding element is expandable progressively inside said recess .

14. Process for giving a rod a final shape of a bolt according to one or more of the previous claims.

15. Mould for giving a rod its final shape, characterised in that it comprises and access channel to the impression of said mould aligned with the axis of said impression, and a thrusters mobile along said access channel to introduce an expanding element along the axis of said rod positioned or thrusted into said impression so as to allow a substantially radial expansion of said rod, suitable for shaping it according to said impression of said mould.

16. Mould according to the previous claim, characterised in that it has heating means of said rod suitable for taking said rod of composite material with a thermoplastic or thermo-setting, respectively, matrix that is not completely polymerised to a temperature in which said matrix becomes mouldable or is completely polymerised, respectively.

17.Mould according to one or more of the previous claims, characterised in that said expanding element has a widened end to form a widened head of the desired configuration for said rod.

18. Mould according to one or more of the previous claims, characterised in that said expanding element has a smooth or threaded side surface to form a smooth or threaded channel along the axis of said rod.

19. Mould according to one or more of the previous claims, characterised in that it has a discharge channel aligned with the axis of said impression suitable for discharging the air inside the mould.

20.Mould according to one or more of the previous claims, characterised in that removable engagement means are foreseen between said thrusters and said expanding element .

21. Mould according to one or more of the previous claims, characterised in that said engagement means are in the form of screw coupling members.

22. Mould for realising a bolt according to one or more of the previous claims.

23. Bolt obtained with a process according to one or more of the previous claims .

24. Bolt according to the previous claim, characterised in that it is made from composite material.

25. Bolt according to one or more of the previous claims, characterised in that said composite material has fibres embedded in a thermoplastic resin-based matrix.

26. Bolt according to one or more of the previous claims, characterised in that said composite material has fibres embedded in a thermo-setting resin-based matrix.

27. Bolt according to one or more of the previous claims, characterised in that said composite material has continuous fibres parallel to the axis of said rod.

28. Bolt according to one or more of the previous claims, characterised in that axially it has an insert.

29. Process for giving a rod its final shape through moulding and rod thus shaped as described and claimed.