THE SAME AND SKATE ROLLER MANUFACTURED BY SAID METHOD

AND/OR IN SAID MOULD.

This invention relates to a method to make skate rollers, to a mould to make skate rollers and to skate rollers manufactured according to such method and/or in such mould.

Skate rollers made by injecting two-component plastic material into two half-moulds, in which a plastic radiate hub has been previously plugged, are known yet.

However these known rollers present some drawbacks, in particular:

the formation of little bubbles in the part near the hub as well as in the surrounding area; some¬ times these bubbles are so big that the roller gets unusable,

the necessity of trimming the excess of matter produced at the end of the injection stage, which leads to a waste of material;

the scarce elasticity of the roller caused by the compact form of the roller itself.

Rollers with a ring-shape tube plugged during the injection stage, putting in evidence an inner tube, are known as well. However it is difficult to plug the tube in the correct position, which is the disadvantage of this kind of rollers.

According to the invention all these drawbacks are elimi¬ nated by a method according to claim 1, i.e. a method to pro¬ duce skate rollers, characterized by the fact that after having poured the plastic material, preferably the polymeric material in the mould of the roller, the mould is simultaneously rotated in correspondence of two axes, orthogonal towards themselves, corresponding respectively to the axis of rotation of the roller and to its diametrical axis.

The practical realization of this invention is here exemplified in a non-restrictive way, with references to the enclosed illustrations, in which

Fig. 1 shows a schematic longitudinal section of a mould to make skate rollers according to the invention.

Fig. 2 shows double-rotation equipment of centrifu¬ gation, and

Fig. 3 shows the longitudinal partial section of a roller produced according to the invention.

As it can be seen, according to a first accomplishment, the procedure in conformity with the invention implies the use of a mould generally indicated with 2 and made with a basic half- -mould 4, a ring-shape half-mould 6 and a locking plug 8 for the central opening of the ring-shape half-mould 6.

The bottom of the basic half-mould 4 has a cylindric match 10 for the trueing up and the positioning of the hub 12 of the roller.

In particular, on the surrounding surface of this hub, which is partially made of plastic material, there are appen¬ dixes 14, which form as a whole a ring-shape hollow 16, which has essentially a semicircular section. Furthermore these appendixes have loop-holes 17.

To accomplish the roller according to the procedure the mould 2 must be taken from a furnace at about 100-120 'C and opened; the hub 12 must be put on the match 10, which is on the bottom of the basic half-mould 4. A ring-shape half-mould 6 must be put on the above-mentioned half-mould 4 and the polymeric material must be injected at a temperature of about

50°C into the ring-shape hollow 18, delimitated by the two half-moulds 4 and 6 and by the ring-shape hollow 16 of the hub.

Particularly, the quantity of injected material is not cor¬ responding to the volume of the ring-shape hollow 18, but it is a smaller one for the reasons further explained.

Successively the mould 2 is closed with the plug 8 and it is assembled on a double-rotation equipment.

This equipment 20 comprises a basic frame 22 that supports two horizontal co-axial shafts 24, one of which is activated by an electric engine 26. These shafts are linked in rotation to a further frame 28, which has two shafts 32 on its vertical rims 30. One of the two shafts is activated by an electric engine 34, which has a larger number of revolutions than that of the electric engine 26. These shafts 32 are linked in rotation to the mould 2.

After the activation of the engines 26 and 34, the contem¬ porary rotation of the mould 2 is caused both along the axis corresponding to the axis of the shafts 24 and along the axis corresponding to the axis of the shafts 32 with consequent centrifugation of the polymeric material put inside the hollow 18.

In consequence of the different speed of rotation of the two shafts 24 and 32 the material inside the hollow 18 places itself mostly on the most exterior surface, consequently forming a ring-shape hollow 36 - essentially with a semicir¬ cular section - inside the above-mentioned material.

Furthermore, the presence of the holes 17 assures a greater adhesion of the material to the hub 12.

At the end of the centrifugation stage the mould is put

again into the furnace at 100-120°C till the complete poly¬ merization of the material.

According to what has been said it is clear that the procedure in conformity with the invention presents several advantages, particularly:

it makes possible the accomplishment of rollers without exterior bubbles, thanks to the centrifu¬ gation that uniformly places the material on the exterior surface;

it makes possible the accomplishment of "lightened" rollers;

it makes possible the accomplishment of rollers that present a high elasticity, thanks to the presence of the inner tube;

it makes possible the use of other materials (for example: gum) with different mechanical features, in addition to polyuretanic materials, or the use of discarded materials mixed with polyuretan with the only function of ligand and so assuring a low cost of production of the roller.

In some cases a fluorescent material can be used, in order to give a pleasant appearence to the roller during the use of the roller-skate.

A different form of accomplishment, not shown in the fi¬ gures, could be that of pouring into the mould a quantity of polymeric material essentially corresponding to the volume of the ring-shape hollow 18. This procedure does not permit to make the inner tube or hollow 36, but it however presents the advantage of making possible the production of rollers without

external bubbles.

Even though the innovating idea so far illustrated is still valid, in the practical accomplishment of the procedure here claimed the possibility of production of a roller without the inner tube has been noted. This roller presents the best features of the current rollers with inner tube, but it has a higher degree of elasticity and it eliminates the greatest drawback of the filled rollers, which ic the presence cf interior or external air bubbles that reduces the efficacy of the roller, often making it unusable.

Moreover, the current filled up rollers present further drawbacks, as it has been described above.

The aim of this innovation is that of accomplishing a procedure that makes possible the manufacturing of filled up skate rollers that are however without interior or external bubbles or hollows, in order to guarantee the best quality of the roller itself.

Another aim of this procedure is that of permitting the greatest elasticity of the roller, even if it is filled up, injecting particular elasticizing elements as well as putting possible fins on the hub that must be covered.

A further aim of this innovation is that of permitting the accomplishment of rollers with a particularly resistant exter¬ nal layer, with a possible tread and also with more elastic and more adherent to the prefabricated hub interior layers, which can be in different colours, in order to give to the roller also a new and original appearence.

Another aim is that of making bindings inside the hub to assure the greatest road-holding quality of the covering.

One more aim of the procedure is that of using the lateral surfaces of the roller to put any tread and also to put in low relief - or to carve - the trade mark or other fancy things.

These and other objects of the invention are achieved by a method according to claim 2, i.e. a method to accomplish skate rollers which is characterized in that in the stage of injec¬ tion of a plastic material, preferably a polymeric material, the mould is put in rotation on the axic cf the previously pressed hub, so that the injected material itself is centrifu¬ gated, the injectors being lowered and pushed towards the moulding hollow, placing itself uniformly in progressive layers till the complete filling up of the hollow itself.

Preferred embodiments of the invention will be explained with six schematic figures in the enclosed sheets, in which

Fig. 4 of sheet 2 shows the axial section of the mould that makes possible the accomplishment of this procedure,

Fig. 5 of sheet 2 shows the plan and partially, the axial section of the previously pressed hub, on which the injection is applied, according to this procedure,

Fig. 6 of sheet 2 shows the same hub of fig. 2 seen from below,

Fig. 7 of sheet 3 shows an axial section of the mould of fig. 4, into which the material has been injected, in order to accomplish the roller according to the innovation,

Fig. 8 of sheet 3 shows the partially sectioned plan of a roller made with this procedure and

Fig. 9 of sheet 3 shows the front of the roller of fig. 8 partially in axial section:

In all figures the same particulars are represented, or are meant to be represented, with the same number of reference.

The improved procedure according to this innovation implies the use of a mould 2 made from a basic half-mould 4, a ring- -shape half-mould 6 and a cone 7 for the locking of the hub 120. The cone has its fulcrum on the match 10 of the base 4. Pipes 9A-9B assure the injection of the two-component plastic material.

Contrary to what is said for the version of the hub already given, this hub 120 has no ring-shape appendixes, but it is equipped with lightening holes 121 as well as possible fins 122, which are linked to a drum - or external surface 124 - and which preferentially have one or more variations in width 123, in order to offer the greatest adhesion surface of the plastic material to inject. For the same reason the drum 124 itself is equipped with external incisions 125, which assure the largest supporting surface between the hub 120 itself and the material to inject.

As a matter of fact this improvement is thought to permit the accomplishment of a roller R, which is without the inner tube and which presents a body completely filled up by the injection, so that it is completely linked to the hub 120.

For this reason, besides the mentioned constructive variations of the hub 120, there is also a different form of the upper ring-shape mould 6, which is combined with the form of the moulding hollow 180 by a particular groove 181, which conveys the injected plastic material, and by a seat 182 on the half-mould 6 for the collection of the possible excess of plastic material.

Finally, the surface of the moulding hollow 180 can be equipped with a carved 183 or in relief 184 and 185 stamp for the reproduction of the trade mark or writings - in relief R or in depth R - or also of the tread B on the resulting roller.

According to this improvement the procedure is generally the same of that already described for times, for temperatures and for the succession of the stages, but it is different for what follows.

Particularly this method implies the use of an equipment of centrifugation of the mould 2, based on only one movement instead of the two previously claimed, namely that on the axis of the hub 120. Consequently the frame of the equipment of centrifugation will be simpler than that already described, which remains however valid for the usable part. This rotation can be transmitted directly to the mould 2 with an adequate transmission of movement, or it can be applied to the cone 7, which, put under pression against the hub 120, gives the wanted speed of rotation to it and to the whole mould 2.

The volume of the material to inject won't be lower than the volume of the housing hollow, since the accomplishment of the inner tube is not necessary anymore, but it must approxima¬ tely have the same - or a bit higher- value of the volume of the hollow 180.

After the description of the used improved parts, also referring to the figures of sheet 2, the innovations of the mothod of accomplishment, proposed in this improvement, are further summarized, also with the help of the figures of sheet 3.

An injector 9A and/or 9B stokes the two-component plastic material, which has the same features already claimed in the patent to improve, and releases it into the groove 181 of the

mould 2, while the mould 2 itself is put in rotation on the axis of the hub 120. To encourage the gathering of the material on the sides of hollow 180, the injectors 9A-9B are advantage¬ ously lowered below the groove 181.

The centrifugal power transmitted to the mould 2 by its rotation dispatches the injected plastic material to the furthermost part of the hollow 180, placing itself in layers till the complete filling up of the hollow 180 itself.

In this stage of filling up the plastic material floods progressively the possible fins 122, assuring, in this way, the largest adhesion surface as well as that on the external surface 124 and its incisions 125, wrapping the whole external part of the hub 120, according to the form of the hollow 180.

The centrifuged application of the plastic material guarantees the constant elimination of the air bubbles, which are gradually removed by the groove 181, assuring the good quality of the roller R in conformity to the main aim of this method.

Naturally the quantity of injected material is approximati- vely calculated to assure the filling up of the hollow 180, while opportune small excesses E of plastic material are con¬ veyed, together with the resulting air of the groove 181 it¬ self, to be placed and released in the groove 182, as indicated in fig. 7.

The particular form given to the part 6 of the mould, which delimits the area between the moulding hollow 180 and the con¬ veying groove 182, assures to the injected material the possi¬ bility of wrapping itself on the drum 124 or external surface 124 of the hub 120, eliminating the excess material, which, as it has been already said, is released into the groove 182. In this way it is given to the roller R a rim which wraps comple-

tely the drum 124 of the hub, without being necessary any mechanical processing of removal of the burrs besides the removal of the moulding excess, for the automatic forwarding of the excess E in the already mentioned groove 182.

At the end of the filling up and of the stage of centrifu¬ gation, completed the stage of polymerization, the roller R is finished with the perfect adhesion of the injected part on the drum 124, with its toothings 125 and its possible fins 122 of the hub 120, assuming a wrapping form of the external drum 124, which is particularly emphesized by the fig. 8.

From the figure 8 itself it can be verified the presence of a stamp R" in relief and an imprint R' as well of a mark of the tread B, casually represented to demonstrate the possibility of accomplishing also signs, writings and graphic reproductions - in relief and/or carved - of trade marks or other advertising writings and of the tread itself.

In particular, the possibility of getting particular de¬ signs of tread B is emphesized, which assures a better road- -holding quality of the roller applied to the roller skate.

The progressive formation of the covering - or roller R - inside the hollow 180, as a result of the centrifugated application of the plastic material emitted by the injectors 9A and 9B, permits also a gradual variation of the quality of the injected material. In particular, one can exemplify the possibility of injecting successively one or more kinds of plastic material - which present different mechanical features -, using one or more injectors 9A and/or 9B, or vary¬ ing the composition to apply with only one injector 9A or 9B. In this way this method assures the possibility of getting an external surface of the roller R with a high resistence to the usage, while its central part can present greater features of elasticity and its central part - in contact with the fins 120

and the drum 124 - can present particular adhesiveness quali¬ ties, combining in a single roller R the best anti-usage, elasticity and adhesion to the hub 120 qualities.

The continuous covering permits also to apply plastic material of different colours, in order to get rollers R with multiformity of colours, which is surely innovating.

This improvement has been illustrated and described according to a particular form of the mould 2 and of the hub 120 as well as following the succession of the production stages.

Fig. 10 and

Fig. 11 of sheet 4 show, a further con¬ structional embodiment of the invention, as it has been mentioned.

According to this solution the attachment of the injected material to the hub 120 beyond that by fins 122 is secured by supplementary spaces 126 formed adjoining to the lightening holes 121. Of course the hub 120 always has a hole passing through 129 and housing seats 128 for the conventional rolling means. With the injection of the covering material the said spaces 126 are regularly filled with the plastic material according to the method of centrifugation already described for forming the connection of the brace-type and the incorporation of the lining R to the hub 120.

Of course variations in the accomplishment of the mould and of the hub and variations or modifications in the manufacturing phases fall within the originality of the procedure wanted to be protected and of the innovating product wanted to get.

Claims