Device and method for the suction of air in injection molds and the subsequent expulsion of molded pieces

Abstract

The device for the suction of air in injection molds and the subsequent expulsion of molded pieces has a Venturi ejector connected to a first valve, that when the mold is closed causes the suction of air in a mold cavity, having at least one insert made from porous material through which and by means of a communication duct that defines a suction circuit, and a second valve, that after the solidification of the plastic material, causes the air to be blown towards the at least one insert made of porous material, cleaning the at least one insert made of porous material. The volume of air to be reduced in the second part of the injection cycle with the same empirical value of 90% efficiency of the Venturi ejector.

Claims

1. A device for the suction of air in injection molds and the subsequent expulsion of molded pieces, comprising a Venturi ejector, a first valve connected to the Venturi ejector configured to suction air in a mold cavity when the mold is closed thereby initiating an injection cycle, a pneumatic double-effect piston in fluid communication with the Venturi ejector and configured to close passage of air in a direction of the Venturi ejector when the first valve is closed; at least one insert made from porous material through which and by means of a communication duct defines a suction circuit, said at least one insert is in fluid communication with the pneumatic double-effect piston; and a second valve in fluid communication with the pneumatic double-effect piston, actuating the pneumatic double-effect piston to blow air towards the at least one insert after the solidification of the plastic material, thereby cleaning said at least one insert made of porous material, wherein upon ending the injection cycle, the first valve that causes the suction of air closes, and wherein upon expulsion of the mold, the second valve enters into operation by making the double-effect piston actuate, closing a passage in a direction of the Venturi ejector, concentrating a pressure only on cleaning the porous material.

2. The device according to claim 1, wherein said at least one insert made of porous material is made of bronze or stainless steel.

3. The device according to claim 1, wherein said at least one insert made of porous material comprises a smooth face and a face provided with a plurality of protrusions.

4. A method for the suction of air in injection molds and the subsequent expulsion of molded pieces using the device of claim 1, the method comprising: actuating the first valve in order to cause the suction of air though the at least one insert made of porous material and the Venturi ejector; injecting plastic material maintaining the suction of air open, during the entire injection cycle; closing the passage of air from the Venturi ejector at the end of the injection, by means of the first valve; allowing the plastic material to cool after the injection until its solidification; activating, at the time of the expulsion of the injected piece, the second valve for blowing air for cleaning the at least one insert made of porous material, wherein upon ending the injection cycle, the first valve that causes the suction of air closes, and wherein upon expulsion of the mold, the second valve enters into operation by making a double-effect piston actuate, closing a passage in a direction of the Venturi ejector, concentrating a pressure only on cleaning the porous material.

5. The method according to claim 4, wherein the suction is performed until a 90% vacuum is reached.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For the purpose of helping to make the foregoing description more readily understandable, it is accompanied by a set of drawings which, schematically and by way of illustration and not limitation, represent an embodiment.

(2) FIGS. 1A and 1B show the double-acting piston and the Venturi ejector of the device according to the present invention, respectively;

(3) FIG. 2 is a diagram of the connections of the device of the present invention according to a first embodiment; wherein the complete diagram of the system already installed in the machine is indicated, where the box A represents the mechanism according to the document ES2348901A1, box B shows the differences incorporated in the present invention, and box C shows the valves of the machine;

(4) FIG. 3 is a schematic view of a mold that the device of the present invention incorporates, according to said first embodiment; and

(5) FIG. 4 is a diagram of the connections of the device of the present invention according to a second embodiment; wherein the diagram of the system already installed in the machine is indicated, where box B shows the differences incorporated in the present invention, and box C shows the valves of the machine.

DESCRIPTION OF PREFERRED EMBODIMENTS

(6) The device according to the present invention preferably comprises two mechanisms installed in the same mold. However, it should be noted that both mechanisms can also work separately, although with different benefits than those described below.

(7) The combined installation is principally intended for large molds, or for molds that, due to their characteristics, require a high technology concept, while separately they can be used for small molds with multiple cavities or for pieces in which the quality of the final product does not need high technical resolution parameters.

(8) In order to describe the complete device such that it is easily comprehensible we refer to the electro-pneumatic mechanism, the same as that in document ES2348901A1, (indicated as A in FIG. 2), while the pneumatic mechanism (indicated as B in the same figure) is the object of the present application.

(9) The pneumatic mechanism B is basically made up of a body preferably made of aluminum, wherein a Venturi ejector 11 is housed, a double-acting piston 10, a silencer 12 and two connections for connecting the compressed air inlets, cleaning air inlet 13 and air inlet 14 from the Venturi ejector. Furthermore, it comprises a connecting nozzle 15 to be coupled in the mold through an O-ring 16, and a pair of screws 17 for its fastening, all of this shown in FIG. 1, wherein the device is shown schematically, wherein it shows the location of the Venturi ejector 11, the double-acting piston 10, the silencer 12, the connecting nozzle 15 for connecting to the mold, the O-ring 16, the air inlets 13, 14 and the position of the fastening screws 17 for fastening to the mold.

(10) FIG. 2 shows that the mechanism A, which is the same as that described in document ES2348901A1, comprises the following elements: a Venturi ejector 1, an internal valve 23, a piston 24, a flow valve 25 and a vacuum gauge 26, the function of which will be described later.

(11) FIG. 2 also shows how the mechanisms A, B stay interconnected in the mold by means of flexible tubes 18 for rapid connection, one connection tube is for supplying the Venturi ejectors 1, 11 that comes from a first valve 21, while the other tube, which comes from a second valve 22, is only intended for the cleaning function of the porous material, the first and second valves 21, 22 being part of the equipment of the mold machine itself.

(12) The method according to the present invention is the following, according to a first embodiment. Upon closing the mold, the first valve 21 that connects the entire internal circuit of the electro-pneumatic mechanism A is actuated. This air flow, upon entering into this mechanism A, is divided into three ducts, a first duct connected to the internal valve 23, through which the piston 24 is activated, which opens the mold aspiration flow valve 25, the second duct connected to the Venturi ejector 1, and the third duct interconnected to the Venturi ejector 11 through the tubes. When the vacuum flow reaches the programmed value, the vacuum gauge 26 activates the internal valve 23 of the mechanism, closing the passage of the mold valve 25 and, therefore, also closing the suction of the Venturi ejector 1. From this point on, we continue suctioning only with the Venturi ejector 11 through a porous insert 31 arranged in the pneumatic mechanism B until the end of the injection cycle. Upon arriving at this point, the first valve 21 is closed, the entire internal circuit of the system thus staying closed.

(13) It is at this point when the expulsion of the mold is activated that the second valve 22 comes into operation, which activates the double-acting piston 10 of the mechanism B, closing the passage in the direction of the Venturi ejector 11, concentrating all its pressure only for cleaning the porous material 31. The blowing-cleaning time can be programmed as necessary.

(14) As shown in FIG. 3, with the aim of taking complete advantage of the entire suction surface of the porous material of the insert 31, it is provided that it already contains a smooth face and a face with small protrusions in its design, in order to, upon being mounted in the punch of the mold, keep some areas of free air circulation, for when suction is performed through the Venturi ejector 1, as well as for when it is time for it to be cleaned. These small protrusions act like a “bed of nails”, in other words they have enough of a contact surface for its fastening, as well as enough of an aerating surface for its perfect functionality.

(15) FIG. 4 shows a second embodiment of the device according to the present invention, in which the electro-pneumatic mechanism A is not present. This embodiment is for a mold with several small cavities, wherein due to the geometry of the product, it does not have areas or enough space to apply the vacuum valve, and only the pneumatic mechanism B can be applied, since, by being a reduced air volume, the direct suction of the Venturi ejector 11 enables the air in these small cavities to be emptied through the porous material of the insert 31.

(16) The operation of the device according to the present invention only with the pneumatic mechanism B is schematically described in FIG. 4. For the sake of simplicity, the same reference numbers are used to identify the same or similar components as in the embodiment in which the electro-pneumatic mechanism B and the machine valves are used. It should be noted that, even though only one insert 31 is shown in FIG. 4, preferably more than one insert 31 will be used, as could be embodied in the first previous embodiment.

(17) The method according to the present invention is the following, according to said second embodiment:

(18) Upon closing the machine, the first valve 21 that gives air to the Venturi ejector 11 is actuated, starting the suction of the air through a circuit that connects to all the cavities. Next, the injection is performed.

(19) From this point on and during the entire injection time, the Venturi ejector 11 continues to apply suction though the inserts made of porous material 31. Upon ending the injection cycle, the first valve 21 that gives air to the Venturi ejector 11 is closed. When the expulsion from the mold is activated, the second valve 22 enters into operation, which makes the double-acting piston 10 actuate, closing the passage in the direction of the Venturi ejector 11, concentrating all its pressure only on cleaning the porous material. The blowing-cleaning time can be programmed as needed.

(20) Despite the fact that reference has been made to a specific embodiment of the invention, it is evident for a person skilled in the art that numerous variations and changes may be made to the device and method described, and that all the aforementioned details may be substituted by other technically equivalent ones, without detracting from the scope of protection defined by the attached claims.