HK1226987A1 - Light-curing oven - Google Patents

Description

Light curing oven

The present invention relates to an oven for photocuring resins.

In particular, the oven according to the invention is useful for photocuring resins applied to the surface of objects manufactured by means of stereolithography processes.

It is known that in order to improve the aesthetic appearance of objects manufactured by means of stereolithography processes, a layer of photocurable resin is applied to the object, which after the photocuring process makes the surface of the object smoother and more uniform.

According to the prior art, the treatment consists in coating the surface of the object with a layer of photocurable resin and then treating the coated object in a photocuring chamber in which a field of photocuring radiation, for example emitted by one or more lamps emitting ultraviolet radiation, is present.

Alternatively, the photocurable resin layer coating the surface of the object may further include moisture automatically generated by the stereolithography process for manufacturing the object.

The curing oven also includes a vacuum pump having a suction inlet in communication with the curing chamber and an electric motor for rotating the object to be treated about a substantially vertical axis of rotation.

The rotation imposed on the object by the motor during the treatment helps to uniformly expose all parts of the surface of the object to the action of the ultraviolet rays in order to obtain an optimal photocuring of the resin coating the object.

Furthermore, the vacuum conditions simultaneously created within the photocuring chamber help to draw gas out of the resin, making the coating denser and uniform, thereby improving the photocuring process.

However, the above-described prior art furnaces have several recognized limitations and drawbacks.

A first recognized drawback is that, as the object rotates about a vertical axis of rotation, the resin coating the object tends to drip at the bottom of the treatment chamber due to gravity and thicken towards the bottommost portion of the object as the object rotates.

Such drawbacks can occur, for example, in devices of the type described in patent DE 202007004266U 1, in which the object is set in rotation about a vertical axis.

Another recognized drawback is that outgassing renders the resin porous, giving the resin a hairy appearance after the treatment is completed.

The limitation resulting from this latter recognized drawback is that the use of ovens according to the prior art does not allow to obtain a smooth surface, which can only be achieved by mechanical polishing by means of grinding tools.

However, mechanical polishing by means of abrasive tools brings about another limitation: mechanical polishing by means of abrasive tools cannot be applied to the inner part of the object, since it is difficult to reach or even impossible to reach the inside of the object.

The known patent US 2014/0013719 a1 describes an oven for curing objects supported on holders that rotate in a "ferris wheel" type movement, thus resembling a rotary movement about a horizontal axis. However, this treatment cannot be performed under vacuum conditions.

Furthermore, the known patent US 5,135,686 describes a continuous curing process.

The present invention aims to overcome all the drawbacks and limitations listed above.

Specifically, a first object of the present invention is to provide a photocuring oven in which a resin to be photocured, which is coated on an object, is less likely to drip onto the bottom of a photocuring chamber during a photocuring process.

Another object of the invention is to ensure that the resin is uniformly distributed over the entire surface of the object during the photocuring process.

An additional but not last object is to ensure that the furnace according to the invention enables objects to be obtained having a smooth and slippery surface.

The above-listed objects are achieved by a light-curing oven with reference to the features described in the independent claim, which is described hereinafter.

Further features of the oven according to the invention and of the photocuring method that can be carried out with said oven are described in the dependent claims.

Advantageously, the oven according to the invention makes it possible to obtain objects with a surface coating having a more uniform thickness than can be achieved with the known photocuring ovens.

Even more advantageously, an object with a smooth surface can be obtained without any mechanical polishing by means of an abrasive tool.

Furthermore, advantageously, the object obtained has a smooth surface, even in the inner part of the object that cannot be reached by the grinding tool and therefore cannot be polished.

The objects and advantages listed above will be better explained by describing a preferred embodiment according to the present invention, provided as a non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 shows an isometric view of a furnace according to the present invention;

FIGS. 2 and 3 show interior elevation views of the furnace of FIG. 1;

fig. 4 shows an interior elevation view of another embodiment of a furnace according to the present invention.

A curing light oven according to the present invention is shown in a shaft side view in fig. 1 and in an interior view in fig. 2 and 3, wherein the curing light oven is generally indicated by 1.

In fig. 2 it can be observed that the oven comprises a structure 1a, inside which structure 1a light-curing chamber 2 is defined and provided with a closable door 2a, and that structure 1a is configured to house one or more objects a coated with the resin to be light-cured.

Inside the light-curing chamber 2 there is a light-curing radiation source 3, which light-curing radiation source 3 is preferably, but not necessarily, attached to the ceiling of the light-curing chamber 2, and which light-curing radiation source 3 comprises one or more UV-ray emitting lamps, for example of the commercially available type.

A light-curing field is thus formed within the light-curing chamber 2, in which the object a is immersed.

The structure 1a defining the furnace 1 according to the invention is substantially parallelepiped-shaped, but in other embodiments it may be any other shape.

Furthermore, the source of light-curing radiation 3 may also be of a different type than the commercially available UV lamps.

The structure 1a comprises a vacuum pump 4, which vacuum pump 4 has a suction duct 5 communicating with the photocuring chamber 2, and the structure 1a further comprises means 6 for moving the object a during the photocuring process.

According to the invention, the movement means 6 comprise an electric motor 7, the electric motor 7 having a drive shaft 8, the drive shaft 8 being mechanically associated with means 9 for supporting the object a to be photocured, the electric motor 7 and the drive shaft 8 being configured so as to cause the object a to rotate about a substantially horizontal rotation axis X.

The support means 9 may vary according to the type of object a to be photocured.

In a related case, and by way of example only, it can be observed in fig. 1 to 3 that the object a comprises a resin ring and is supported by a support device 9, the support device 9 comprising a plate 9a and a plurality of gripping members 9b, the plate 9a being coupled to the drive shaft 8 of the electric motor 7, the plurality of gripping members 9b being attached to the plate 9a and each of the gripping members supporting the object a.

Obviously, the shape and size of the support means can be varied to accommodate different types of objects, in particular objects of different shapes and sizes.

Effectively, the oven according to the present invention is used to cure the resin coated on the surface of the object a to make the resin smooth and uniform.

For this purpose, the surface of the object a is coated with a photocurable resin which is applied by spraying or immersion or by other means.

Alternatively, as mentioned previously, the photocurable resin layer coated on the surface of the object may include moisture spontaneously generated by the stereolithography process in which the object is manufactured.

Each object a is placed inside a light-curing chamber in which it is associated with a support device 9 and, in this particular case, with a respective gripping member 9 b.

Subsequently, the door 2a of the photo-curing chamber 2 is closed, the photo-curing radiation source 3 is opened, and the vacuum pump 4 and the electric motor 7 are turned on.

During the rotation about the horizontal axis X, all portions of each object a are exposed to the photocuring action of the radiation source 3 for the same amount of time, which ensures a complete and uniform photocuring of the resin on all portions of the surface of the object a.

Further, the rotation speed of the electric motor 7 can be adjusted to such a value that the time taken for each object a to complete a half rotation is less than the time taken for the applied resin to escape due to gravity, so that it is possible to avoid the resin from dripping onto the bottom 2b of the light curing chamber 2, thus achieving one of the objects of the present invention.

Finally, the rotation of the object a about the horizontal axis X prevents the formation of resin accumulation zones, thus achieving another object of the invention, namely to obtain a photocured coating of uniform thickness.

Since the photocuring treatment is carried out under vacuum conditions, a further object is also achieved: a dense and uniform surface coating on the object is obtained, since the gases contained in the coating are released.

Thus, the obtained surface is smooth and uniform in thickness, but the presence of microbubbles generated by the gas gives the obtained surface a hairy appearance due to spontaneous generation of gas from the resin caused by the negative pressure inside the photocuring chamber 2 during the photocuring process.

In order to overcome this drawback and form a smooth surface coating on the object, it is necessary to eliminate the formed microbubbles during the photocuring process by continuously compacting the resin coated on the object a.

To this end, as shown in fig. 2, the movement means 6 also comprise means 10 for vibrating the object a, which means 10 comprise one or more piezoelectric transducers 11 of a known type on the market, said one or more piezoelectric transducers 11 being associated with the base 7a of the electric motor 7 or with the base 1b of the structure 1a of the oven 1, as shown in fig. 3.

The vibrating means may also comprise an ultrasonic generator associated with the base 7a of the electric motor 7 or with the base 1b of the structure 1a of the oven 1.

Another embodiment of the oven according to the invention is shown in fig. 4, generally designated by the reference numeral 100, wherein it can be clearly observed that the oven 100 differs from the previous embodiments in that the moving means 106 comprise an electric stepping motor 107 and a vibrating means 110, the vibrating means 110 comprising an electronic control means 112 provided with programmable logic, the electronic control means 112 being configured to operate the stepping motor 107 to define a rotary motion.

The rotational movement may comprise a plurality of rotations all in the same rotational direction, or the rotational movement may comprise a plurality of rotations in opposite rotational directions.

In all the embodiments described, the vibration motion compacts the resin coated on the object, since the vibration motion breaks micro-bubbles generated by gas spontaneously emerging from the resin due to the vacuum condition in the photo-curing chamber 2.

Thus, at the end of the photocuring process, the object surface will become smooth, thereby achieving another object of the present invention.

Combining the oscillating movement of the object a with the rotation of the object about the axis X makes it possible to achieve a surface coating which, in addition to having a uniform thickness over the entire surface of the object and a smooth, dense and uniform photocured appearance, is also smooth, unlike the results obtained with photocuring ovens according to the prior art.

Thus, an object having a smooth surface can be obtained without relying on any manual polishing by means of a mechanical grinding device.

And also a smooth surface is obtained on all parts of the object a, even the internal parts of the object that cannot be reached by the mechanical polishing means.

The photocuring oven according to the present invention enables a photocuring method including the following operations to be sufficiently performed:

-coating the surface of the object to be treated with a layer of photocurable resin;

-arranging the object in a light-curing chamber;

-forming a field of photocuring rays within a photocuring chamber;

-forming a vacuum within the photocuring chamber;

-rotating the object within the light-curing chamber about a substantially horizontal axis of rotation.

The method may further comprise simultaneously vibrating the objects.

Based on the foregoing description, it is thus clear that the curing oven according to the present invention enables the achievement of the intended objects and advantages.

Any modifications and variations made to the curing oven and curing method within the scope of the appended claims should be considered protected by this patent.

Claims (12)

1. A photo-curing oven (1; 100) comprising:

-a light-curing chamber (2), said light-curing chamber (2) being configured so as to be able to house one or more objects (a) to be light-cured;

-a source of light-curing radiation (3), said source of light-curing radiation (3) being arranged inside said light-curing chamber (2);

-a vacuum pump (4), said vacuum pump (4) having at least one suction duct (5) communicating with said photocuring chamber (2);

-moving means (6; 106), said moving means (6; 106) being adapted to move said object (A) during a photocuring process,

characterized in that said movement means (6; 106) comprise at least one electric motor (7; 107), a drive shaft (8) of said electric motor (7; 107) being mechanically associated with support means (9) adapted to support said object (A) to be photocured, said electric motor (7; 107) and said drive shaft (8) being configured to define a substantially horizontal rotation axis (X) of said object (A).

2. Curing oven (1; 100) according to claim 1, characterized in that said moving means (6; 106) further comprise vibrating means (10; 110) adapted to vibrate said object (A).

3. Curing oven (1) according to claim 2, characterized in that said vibrating means (10) are associated with the base (7a) of said electric motor (7).

4. Curing oven (1) according to claim 2, characterized in that said vibrating means (10) are associated with the base (1b) of the structure (1a) of the oven (1).

5. Photocuring oven (1) according to claims 2 to 4, characterized by the fact that the vibrating means (10) are one or more piezoelectric transducers (11).

6. Photocuring oven (1) according to claims 2 to 4, characterized by the fact that said vibrating means comprise an ultrasonic generator.

7. The curing oven (100) of claim 2, wherein the electric motor (107) is a stepper motor, and the vibration device (110) comprises an electronic control device (112) provided with programmable logic, the electronic control device (112) being configured to be able to operate the stepper motor (107).

8. The curing oven (100) of claim 7, wherein the rotational movement comprises a plurality of rotations all in the same rotational direction.

9. The curing oven (100) of claim 7, wherein the rotational movement comprises a plurality of rotations in opposite rotational directions.

10. Curing oven (1; 100) according to any of the preceding claims, characterized in, that the curing light source (3) comprises one or more UV ray emitters.

11. A photocuring method for photocurable resin that is applied so as to cover a surface of an object disposed within a photocuring chamber of a photocuring furnace, the method comprising the operations of:

-covering the surface of the object with the layer of photocurable resin;

-arranging the object within the light-curing chamber;

-forming a field of photocuring rays within the photocuring chamber;

-forming a vacuum within the photocuring chamber;

-rotating the object within the light-curing chamber;

characterized in that said rotation of said object is performed about a substantially horizontal rotation axis.

12. The method of claim 11, wherein the object is vibrated during the rotating.