Technical field

The present invention relates to a device for injection of wax into the mold, particularly by lost wax casting in jewelry, silver and costume jewelry, and to its injection process.

Background Art The lost wax casting is an industrial process which involves molding by models in a material that can be easily melted, such as wax or thermoplastic resins, which are liquefied once the piece to realize is formed and the molten metal is poured into the mold.

By means of this process, complex objects are obtained, even the ones with a high degree of finishing and accuracy, however a model for each copy of the object is required.

For the realization of articles of jewelry, silver and costume jewelry, models are prepared by wax injection or using thermoplastic resin, or other equivalent materials, on suitable silicone rubbers. At the state of the art, wax injectors are known, in which a manual loading of the rubber mold in the caliper of the injector is provided by the operator. The operator, once the injection cycle has completed, will remove the mold from the caliper to cool down the model wherein the mold, so that it can be removed after the wax solidifies. Although the cooling can be accelerated with cooling means (refrigerators, fans, etc.), nonetheless, waiting times for cooling down the mold are often very long, and given that for each item to be produced it is necessary a wax model to be liquefied, for large productions it will be needed a very wide stock of molds- waxes, so as not to have problems in the event of sudden orders, with all the difficulties that this entails.

For example, it can happen that the cooling takes place rather quickly, i. e. in case of small pieces, and thus removing the wax from the mold is faster than the time necessary to the machine for a new injection of the wax into the mold, or, on the contrary, it can happen that the machine be stopped for several seconds while the operator removes the wax from the mold for the next injection.

In addition, the production costs of such pieces are high in view of the fact that, in practice, an operator must be completely dedicated only to the injection of the wax in the rubber molds.

This injection system, rather artisan, is overcome by semiautomatic injectors which provide to locating the molds on a first conveyor belt, which carries each mold in front of the injector, pushes the grip that injects the wax, removes it from the caliper and transports the mold, with the injected model inside, to a storage area by means of a second conveyor belt.

These semi-automatic injectors, however, present logistical difficulties related to their overall dimensions, due to the fact that the surface occupied by the conveyor belts is often inadequate in goldsmith workrooms. In addition, the waiting times for cooling down the model, before it can be removed in solidified form from the inside of the mold and be proceed to the next injection, are always very long and uncertain.

Another drawback of these injectors is the fact that it is still necessary the presence of a dedicated operator, which has to manage the cooling/extraction/injection timing and to control the orderly functioning of the production line.

Disclosure of the Invention

The object of the present invention is to eliminate the drawbacks noted above in known types of device to inject wax into the mold, particularly by lost wax casting in jewelry, silver and costume jewelry, that allows to automate the process of injection wax into molds.

Within this aim, an object of the present invention is to provide a device for injection of wax into the mold, which strongly limits the presence of a dedicated operator, in order to reduce production costs.

It is another objective of the present invention to optimize the cooling time of the model in order to synchronize the model extraction and the wax injection into the mold.

It is therefore to be expected to provide a device for injection of wax into the mold, particularly for lost wax casting in jewelry, silver and costume jewelry, so that the device is economically competitive and easy to assemble.

This aim and these and others objectives which will become better apparent hereinafter, are achieved by a device for injection of wax into the mold, particularly for lost wax casting in jewelry, silver and costume jewelry, comprising an injector of plastically deformable material to hot molds, said molds being arranged to be filled with said plastically deformable material to create a model, characterized in that said injector is connected, by means of supply means, to a stock of molds extending along a vertical direction substantially normal to the ground, and is also connected, by expulsion means, to a cooling plate, defining a plane substantially normal to the ground.

Brief description of the drawings

Further characteristics and advantages of the invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of the injection device of wax into the mold, particularly for lost wax casting in jewelry, silver and costume jewelry, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 represents the injection device of wax into the mold, particularly for lost wax casting in jewelry, silver and costume jewelry, in elevation; Figure 2 represents the device of figure 1, in rjlan;

Figure 3 shows the gripper 7 of the injector 2 of the device of figure 1, in perspective view.

Modes for carrying out the Invention

With reference to the above figures, the device of injection of wax into the mold, particularly by lost wax casting in jewelry, silver and costume jewelry, according to the invention, which is identified in its entirety by the reference 1, comprises an injector 2 of plastically deformable material in hot molds, such as wax or thermoplastic resins. The molds are arranged to be filled with such a wax to produce a model. A primary feature of the invention is due by the, fact that the injector 2, which is known per se, is connected, by supply means, to a stock of molds 3 which extends along a vertical direction 10, which is substantially normal to the ground. Furthermore, the injector 2 is connected, by expulsion means, to a cooling plate 4, which defines a plane substantially normal with respect to the ground.

In the present embodiment, injector 2, stock of molds 3 and the plate 4 are supported by a supporting frame 12 arranged to lean on the ground.

The stock 3 has an inlet 13 and an outlet 14, which may include a pilot hole to provide for the mold to be filled inside the injector 2 in the more precise manner as possible.

The inlet 13 has such dimensions as to prevent the simultaneously passage of two standard measuring molds, in such a way that the second mold, which would be loaded later, that is located above the mold to be filled, is blocked by the walls of the stock of molds 3.

On the contrary, the outlet 14, has an opening which is higher and wider than the standard sizes of the molds, in order that molds of different measurements can pass through.

Preferably, the height of the outlet 14 is adjustable by means of a door which is slidably engaged, by means of a slot, on a wall of the stock 3.

Advantageously, the supply means provide a first actuator 5 connected to the molds stock 3, which can move between the base of said stock 3 and the gripper 7 for clamping the molds to the injector 2. Said actuator 5 is arranged to be translated along a feed direction 20 of the injector 2, which is substantially normal to the vertical direction 10, passing through the inlet 13 and the outlet 14 of the stock of molds 3.

In our embodiment, the actuator 5 has a bracket 15 shaped as a chute.

Once the piston has done to load, the mold returns back to the stop and, at this point, the mold that was above falls into the bottom of the stack, ready to be pushed.

In the present embodiment, the stock of molds 3 is provided with locking means for the first actuator 5, when the operator's hand or other impediments are close by. For example, such locking means may comprise photocells, or other types of sensor means, which prevent that the mold is loaded into the injector 2 by detecting the presence of the operator's hand.

Obviously, when the hand, or another obstacle that blocks the loading is removed, the actuator 5 begins to feed the injector 2. In automatic operation mode, the device works without the need to activate a start key by just removing the hand or other impediment to the loading.

The gripper 7, which as shown in Figure 3, is developed in a direction substantially normal with respect to the ground (that is to say substantially parallel to the vertical direction 10). It is provided with means for automatic centering of the mold, comprising a pair of harmonics springs, funnel positioned. During the loading phase of the mold in the gripper 7, the springs center the mold while it is passing between them. Advantageously, said expulsion means comprise a rod 11 pushes against the filled mold, so that this filled mold rotates about 90° aligning its long side in a direction substantially normal with respect to the direction of development 40 of the plate 4. With reference in particular to Figure 3, the rod 11 can develop in a direction substantially parallel to the direction of expulsion 30.

Advantageously, the expulsion means comprise at least a second actuator 8, connected to the gripper 7, for the removal of the mold filled with wax, thermoplastic resins or other plastically deformable material, by the injector 2 towards the cooling plate 4. The actuator 8 is arranged to be moved between the injector 2 and the cooling plate 4 along a direction of expulsion 30 which is substantially normal to the vertical direction 10.

The actuator 8 may be provided with a plate 21 connected to an anti-rotation stem 22. With reference to the enclosed figures, the direction of expulsion 30 is also substantially normal to the feed direction 20.

In practice, the mold is rotated by the rod 11 and, immediately after, is removed from the actuator 8 to go on the plate 4.

A technically equivalent solution will be the one that provides, for the first thing, the movement of the mold from the injector 2 to the plate 4 thanks to the actuator 8, and then the push of the rod 11 to rotate it.

It can be expected that the direction of development 40 is substantially normal with respect to the direction of expulsion 30, in a manner that it forms a kind of "U" and, therefore, the loading position of the of operator for filling the molds into the stock 3 will be substantially the same with the unloading position of the molds filled and cooled.

Advantageously, the cooling plate 4 has at least one Peltier cell, known per se, associated to the lower face of the plate with respect to the ground. The cooling plate 4 advantageously comprises a third actuator 9, having for example a pusher 24 arranged to translate along the direction of development 40, to align the filled mold and minimize space.

The plate 4 preferably has an end stop 19 in its peripheral portion opposite to where the actuator 9 is mounted, in such a way that, when it is full, the cycle is automatically stopped. Of course, as soon as the mold is removed from the end stop, if there are other molds to be filled in the stock of molds 3, the device restarts automatically.

This end stop can be disabled simply by stretching the plate 4 with an auxiliary plane. Once rotated the rod 11 make the mold slide on the plate 4 pushing it to leave space for the next mold in such a way that the sequence can be continuous.

Advantageously, automation means are provided for the operation of the device controlled by a logic unit, such as a computer program, an electronic card equipped with a timer or clock, and other similar means. Preferably, these automation means comprise a reader of micro-chip, which is arranged to read the parameters for the injection contained within a microchip positioned in each of the molds. This reader is mounted on the base of the stock of molds 3. Even the cooling temperature of the Peltier cell of the plate 4 can be set by the logic unit.

Preferably, the cooling temperature is read by a sensor, i. e. a NTC type that returns the value of the temperature to an electronic card and which, through a PID controller, controls the temperature through the switching on and off of the Peltier cells.

As an alternative to the micro-chip, it is possible to set a program the same for all the molds, in such a way that, where a simple detection sensor notices the presence of molds, starts the loading of the molds from the sock of molds 3 to the injector 2. In this case, however, the models of rubbers must be very similar to each other, that is to say that they will have to present the same parameters for all.

The logic unit controls the whole movement of the actuators, controls the photocell for detecting hands or other impediments, manages the temperature of the cooling plate 4 as well as actuates the end stop, by means of electro- valves.

The method of injection of a plastically thermo-deformable material into molds to produce a model, characterized by the succession of steps consisting in:

- loading a stock of mold 3 which extends along a vertical direction 10 substantially normal with respect to the ground,

- reading the parameters of injection by means of a logic unit connected to the device, for example by micro-chips associated to the molds, - feeding an injector 2 by means of a first actuator 5 in movement between the base of the stock of molds 3 and the injector 2, along the feed direction 20, substantially normal to the vertical direction 10,

- injecting the wax, the thermoplastic resin or other plastically deformable material within the mold to fill - once the gripper 7 has obviously been closed -, in order to create a model by filling the empty parts within the mold itself, by means of a nozzle 6 defined in the injector 2,

- rotating the filled mold with about 90° aligning the long side in a direction substantially normal with respect to the direction of development 40 of the plate 4, by means of a push rod 11. The direction of development 40 is substantially normal with respect to the direction of expulsion 30 ,

- ejecting the mold thus filled with wax by means of a second actuator 8 of removal of the mold from the injector 2 to a cooling plate 4 along the direction of expulsion 30, which is substantially normal with respect to the vertical direction 10 and substantially normal to the feed direction 20. The plate 4 defines a plane substantially normal with respect to the ground,

- aligning the filled mold by means of a third actuator 9 of translation along the direction of development 40, and

- cooling the filled mold on the cooling plate 4. Practically, once the molds have been loaded in the stock of molds 3, the device is started by actuating on its logic unit, for example by means of an interface (screen, button, etc.) or automatically as soon as the hand is removed from the photocell. At this point the microchip reader recognizes the presence of the mold and reads the parameters of injection.

The actuator 5 goes to load the mold to be filled in the gripper 7 of the injector 2. The mold, passing from the centering means, is positioned in the vicinity of the nozzle 6. In the meantime, in the stock of molds 3, while the first actuator 5 returns back, the mold to be filled later, which was located in the stock of molds over to the mold that is filled, down in the bottom of the charger ready to be moved towards the injector 2.

After injection, the gripper 7 is opened, the rod 11 rotates the mold thus filled and the actuator 8 unloads it in the cooling plate 4.

At this point the third actuator 9 slides automatically the filled mold on the plate 4 and, simultaneously, the cycle starts again and is repeated until all the elements present in the stock of molds 3.

From what has been described above it is therefore evident that the invention achieves the proposed aim and objectives and, in particular, the fact is stressed that a device is provided for injection of wax into the mold, particularly by lost wax casting in jewelry, silver and costume jewelry, which allows to automate the process of injection wax into molds.

In particular, since the operator is not forced to manually put the mold in the gripper, as well as to remove it subsequently, the process of injection is much faster because these steps are done automatically by the machine.

Another advantage of the invention is given by the substantial increase in production thanks to the system of loading and unloading of the mold into the gripper, to the automatic starting and to the cooling system. Moreover, limiting the time and the activity of the operator on the device, there is a substantial cost reduction.

Another advantage of the invention is due the fact that, the optimization of the cooling times of the model, in such a way that it is possible to synchronize the operations of extraction of the model and injection of wax into the mold.

Another advantage of the invention is given by the cooling system with cooled plate by Peltier effect that not only it does not affect the quality of the wax of the model, but it speeds the production as by cooling the mold, increases the speed of solidification of the wax at its inside after the injection, and then decreases the waiting time to extract the wax model and put back the empty mold in the charger.

Another advantage of the invention is the fact that the device is able to work continuously, as long as there are molds in the stock of molds to be loaded, for this reason it is no longer necessary for the operator removes the wax from the mold previously injected to put it in the gripper before starting the production cycle and, vice versa, the operator need not wait until the device has finished inject before loading other molds to be filled: in this way the dead times are reset by a considerable reduction of production costs.

Furthermore, another advantage of the invention, is the fact that, having used actuators for moving the mold, i.e. commercial pistons, the use of belts driven by motors, that have higher costs and overall dimensions, are avoid.

Another advantage of the device is given by the particular shape of the stock of molds, being in practice vertical, together with the U-shaped moviment given to the mold during the filling cycle, allows the realization of a compact and less expensive machine. Not least, the use of means readily available commercially and the use of common materials, make the device economically competitive.

Although the disclosed embodiments have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed embodiments as defined by the appended claims.

The invention thus conceived is susceptible to numerous modifications and variations, all falling within the inventive concept, and all the details may further be replaced by other technically equivalent elements.

In practice, the materials used, as well as the dimensions, may be any, according to requirements.

Where technical features mentioned in any claim are followed by reference numbers, those reference numbers have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference numbers do not have any limiting effect on the interpretation of each element identified by way of example by such reference numbers.