Systems for operating fluid actuators

Abstract

A system (MC1; MC2) is described, comprising an actuator having a linearly movable piston (14) and a needle valve (12) connected to said piston (14) for adjusting the injection flow rate of molten material from a nozzle to a mold. Pressurized fluid is brought to the piston (14) via supply circuits (30, 32) to reciprocate it. Solenoid valves (60; 70) are connected to said supply circuits (30, 32) and configured to open a fluid discharge path in a resting state to bring the valve to a closed position.

Description

Technical Field

[0001] The present invention relates to a system for operating a fluid actuator, and more particularly to a system for adjusting / changing the stroke of a piston included in a fluid actuator. Background Technology

[0002] Taking an injection molding machine as an example, molten material is injected into the mold through one or more injection nozzles. The opening and closing of the nozzles is adjusted by one or more valve stems, which are controlled by actuators. For complex or large parts produced by multiple injections and / or sequential injection methods, the position control of the valves opening and closing the nozzles is crucial for achieving high-quality surface finishes, especially for controlling the flow rate of molten material and the injection pressure in the mold cavity. Currently, for molding high-value products, valves are controlled by electric actuators (because they allow for a wide range of adjustment and control), but electric actuators require complex and expensive control devices (electronic control unit + related software + sensors + complex wiring + professional operators). Therefore, for some applications, the use of fluid actuators is more convenient and familiar to the user, see, for example, EP3490777. Figure 2 The system typically uses a three-way solenoid valve 20 to control the actuator 1 via a fluid circuit.

[0003] One problem is that in the event of a sudden power outage or emergency, solenoid valve 20 moves to the central rest position (determined / set by the action of springs 220 and 230), thereby locking the valve in its current position and keeping the injection channel open. This obviously creates a potentially dangerous situation and can cause considerable damage to the injection system. Summary of the Invention

[0004] The main objective of this invention is to improve upon existing technologies.

[0005] Another objective is to improve the system by making it safer, particularly by allowing the valves to reposition to the closed position in the event of a power failure, as in the system in EP3490777.

[0006] One aspect of the present invention relates to a system comprising:

[0007] - An actuator, which is provided with a piston movably mounted to move linearly within two chambers separated by the thrust of a fluid.

[0008] - A needle valve, which is connected to a piston, to adjust the flow rate of molten material ejected from one or more nozzles into the mold.

[0009] This allows the valve to move from a closed position where no molten material passes through the nozzle to an open position where molten material passes through the nozzle.

[0010] - A supply circuit for carrying pressurized fluid from the reservoir to the chamber in both directions of flow, corresponding to the forward and backward motion of the piston, respectively.

[0011] - A solenoid valve, which is connected to the supply circuit and configured to open the fluid discharge path connecting the chamber and the reservoir in the resting state to allow fluid to flow between the chamber and the reservoir, thereby causing the piston to move to bring the valve to the closed position.

[0012] Multiple needle valves can be connected to the piston so that they can move synchronously by the piston.

[0013] In one variant, the system includes

[0014] - The main circuit that constitutes the power supply circuit, and

[0015] - A fluid bypass pipe that forms the discharge path, arranged to bypass the main loop.

[0016] The solenoid valve is inserted into the path of the bypass pipe, preferably including an actuated position where it closes the fluid discharge path.

[0017] Preferably, the bypass conduit path includes one or more check valves to ensure the flow direction of fluid in the bypass conduit.

[0018] Preferably, the system includes a second solenoid valve connected to the supply circuit and comprising...

[0019] - Two incentive positions:

[0020] In the first position, the second solenoid valve allows fluid communication between the chamber and the reservoir by applying a flow direction to the fluid in the supply circuit.

[0021] In the second position, the second solenoid valve allows fluid communication between the chamber and the reservoir by applying a fluid flow direction in the supply circuit opposite to the fluid flow direction available in the first position.

[0022] - Rest position, in which the second solenoid valve prevents fluid communication between the chamber and the reservoir.

[0023] The second solenoid valve may also include only one of the two actuation positions. To allow for two fluid flow directions, two such solenoid valves can be placed in parallel.

[0024] In one variation, the solenoid valve is inserted directly into the path of the supply circuit.

[0025] Specifically, the solenoid valve includes two actuation positions:

[0026] - It allows fluid communication between the chamber and the reservoir by applying a fluid flow direction in the supply circuit that is opposite to the fluid flow direction available at the resting position, and

[0027] - It is the location that prevents fluid communication between the chamber and the reservoir.

[0028] Alternatively, two solenoid valves can be directly inserted into the supply circuit path, each with an actuated position, whereby they allow fluid communication between the chamber and the reservoir by applying a fluid flow direction in the supply circuit opposite to the fluid flow direction obtainable from the other solenoid valve.

[0029] The fluid can be a liquid, such as oil, or compressed air. Attached Figure Description

[0030] The advantages of the invention will become clearer from the following description of the preferred system with reference to the accompanying drawings, in which:

[0031] · Figure 1 The system scheme is shown.

[0032] · Figure 2 A variation of the system scheme is shown.

[0033] In the diagram, identical components are indicated by the same labels. Detailed Implementation

[0034] Figure 1 The system MC1 is used to drive actuator 10. Actuator 10 is attached to a support such as a hot runner (manifold) or plate or mold, and is used to move (directly or indirectly, through an mediated motion conversion mechanism - not shown) at least one needle valve 12 for an injection nozzle (not shown) by means of piston 14. Piston 14 is linearly movable within a cavity defined by housing 16. This cavity is divided by piston 14 into a first chamber 20 communicating with port 22 and a second chamber 24 communicating with port 26. Chamber 20 is normally isolated from chamber 24; however, situations may arise where it is necessary to provide a means for connecting the two chambers.

[0035] Fluid (e.g., oil or compressed air) can be injected into or extracted from chambers 20 or 24, respectively, on opposite sides of piston 14 through fluid ports or inlets 22, 26, so that piston 14 can move linearly in opposite directions, thereby moving valve 12 accordingly. The movement of valve 12 determines the opening or closing of nozzle, thereby causing the passage or blockage of molten material.

[0036] The opening and closing of the nozzle, and thus the movement of the valve (pin), can occur based on a single movement in both directions (with a tendency for a single opening ramp and a single closing ramp), or may include multiple different intermediate stops (motion pauses according to preset parameters, after which the movement restarts according to previous parameters (speed, pressure, flow rate, etc.) or according to modified parameters). During the opening or closing movement, infinite motion pauses can be achieved based on an infinite number of positions.

[0037] The fluid circuit allows fluid to be pumped into and out of chambers 20, 24 from an external reservoir (not shown, such as a tank). The circuit includes a first line 30 and a second line 32. Optional flow regulators 40, 42 are also included in lines 30, 32, which, in addition to uniform motion, allow for different speeds of movement of the piston 14 along its stroke.

[0038] The flow regulators 40 and 42 can be activated manually or automatically. In the latter case, they can be adjusted according to a predetermined position or based on position feedback given by a suitable position sensor (not shown) for the valve or piston.

[0039] A solenoid valve 50 with a movable drawer / pull-out component 52 is used to reverse the direction of fluid flow in lines 30, 32 during each complete cycle. The flow direction determines the direction of movement of piston 14 and thus valve 12 during opening or closing.

[0040] For this purpose, the solenoid valve 50 can be electrically switched to two different actuated positions, in which it allows fluid to flow from the reservoir to the actuator 10:

[0041] - In one position, a portion of the fluid can flow along pipeline 32 into chamber 20, and a portion of the fluid can flow out of chamber 24 into pipeline 30 (valve 12 moves toward the closed position), and

[0042] - In another location, a portion of the fluid can travel along line 30 into chamber 24 and fluid can flow out of chamber 20 into line 32 (valve 12 moves toward the open position).

[0043] When at rest, solenoid valve 50 remains in the position that prevents fluid from flowing in lines 30, 32, so piston 14 remains stationary.

[0044] The solenoid valve 50 is, for example, a commercially available type with an excitation coil and a return spring.

[0045] In the event of an unexpected power supply voltage failure and / or emergency, solenoid valve 50 will switch to the center position, thereby stopping fluid flow and creating a critical safety state in the system as described in the introduction due to the immediate cessation of valve 12 (regardless of its position).

[0046] To facilitate the closure of valve 12 and eliminate inconvenience under all circumstances, system MC1 includes fluid bypass pipes 62, 64 that bypass lines 30, 32 toward the fluid reservoir. Pipes 62, 64 terminate at solenoid valve 60, which has a drawer-type component that can be electrically switched between two different positions.

[0047] - In the rest position, solenoid valve 60 allows fluid in lines 30 and 32 to be transferred out of and into the reservoir, and

[0048] - In another position, solenoid valve 60 is energized, and fluid flow is blocked.

[0049] One-way valve 66 is inserted into pipes 62 and 64.

[0050] Preferably, system MC1 includes an electronic control unit (not shown) to control at least solenoid valves 50, 60 and a pump for moving fluid. Automatic control of flow regulators 40, 42 can also be implemented.

[0051] During normal operation of system MC1, in the presence of voltage, the electronic control unit energizes solenoid valves 50 and 60. Solenoid valve 50 is then controlled to adjust the fluid flow rate and direction in lines 30 and 32 (to move piston 14), while solenoid valve 60 blocks flow in lines 62 and 64.

[0052] In abnormal conditions, or in the absence of voltage, the electronic control unit de-energizes solenoid valves 50 and 60. Solenoid valve 50 then blocks flow in lines 30 and 32, but solenoid valve 60 allows fluid flow in lines 62 and 64, including:

[0053] Fluid flows out of chamber 24 and through pipeline 64, and

[0054] Fluid flows into chamber 20 and through pipeline 62.

[0055] This fluid flow allows the valve 12 to be moved to the closed position, thus providing a safe position for the valve 12.

[0056] A more compact and simpler variant of system MC1 is Figure 2 The system MC2 in the middle.

[0057] Solenoid valve 50 and associated piping 62, 64 are removed, and solenoid valve 50 is replaced by a different solenoid valve 70, which has a drawer-type component 72 that can be electrically switched between two actuated positions.

[0058] - In the first position, some fluid can travel along pipe 30 toward chamber 24 and some fluid can flow out of chamber 20 along pipe 32, and

[0059] - In the second position, fluid flow is suppressed.

[0060] When at rest, the solenoid valve 70 is held in a position that allows fluid to flow through line 32 into chamber 20 and out of chamber 24 into reservoir via line 30.

[0061] It should be understood that system MC2 is inherently safe because the solenoid valve 70 automatically configures (or trips) under abnormal conditions or in the absence of voltage, allowing fluid to flow in lines 30 and 32 to bring valve 12 to the closed position.

[0062] Please note that the command sequence sent to solenoid valves 50 or 70 is different in order to obtain the same dynamic curve for valve 12. Specifically, in Figure 2 middle:

[0063] In order to raise valve 12 and open the channel for molten material, solenoid valve 70 is energized to place solenoid valve in the first position;

[0064] In order to lower valve 12 and close the passage, solenoid valve 70 is de-energized;

[0065] In order to keep valve 12 in the middle position, solenoid valve 70 is energized to move solenoid valve to the second position.

[0066] Generally, energizing solenoid valve 70 is for...

[0067] Keep valve 12 in the middle position, and

[0068] The valve 12 moves in only one direction.

[0069] exist Figure 1 and 2 In this case, solenoid valve 50 or 70 can be replaced by a pair of bidirectional solenoid valves with the same rest configuration.

[0070] In both cases, by properly managing the open or closed position of the piston's supply circuit, thereby managing the different positions of the solenoid valve and potentially regulating the flow regulator, the invention as described above allows for the making / implementation of one or more of the open and / or closed curves described and illustrated in the following documents:

[0071] PCT / IB2019 / 053936, IT102017000037002, IT102016000080198, IT102016000055364, IT102015000008368, ITTO2014A001030, ITTO2014A001021, ITTO2014A000701, WO2012 / 074879A1, WO2012 / 087491A1 and WO2018 / 020177A1.

Claims

1. A system comprising: - An actuator (10) provided with a piston (14) movably mounted to move linearly within two chambers separated by the piston (14) by the thrust of a fluid. - A needle valve (12) connected to the piston (14) is used to adjust the injection flow rate of molten material from the nozzle to the mold. This allows the valve to move from a closed position where no molten material passes through the nozzle to an open position where molten material passes through the nozzle, and from the open position to the closed position; - A supply circuit for bringing pressurized fluid from the reservoir to the chamber in the flow direction and the opposite direction, the two fluid flow directions corresponding to the forward and backward movement of the piston (14), respectively; and - A solenoid valve, which is connected to the supply circuit and configured to open the fluid discharge path connecting the chamber and the reservoir in the resting state to allow fluid to flow between the chamber and the reservoir, thereby determining the movement of the piston to bring the valve to the closed position.

2. The system according to claim 1, comprising: - The main circuit constituting the supply circuit, and - A fluid bypass pipe constituting the discharge path is arranged to bypass the main loop. The solenoid valve is inserted into the path of the bypass pipe.

3. The system according to claim 2, wherein, The bypass pipeline path includes one or more check valves (66).

4. The system according to claim 2 or 3, further comprising a second solenoid valve (50) connected to the supply circuit and comprising: - Two incentive positions: In the first position, the second solenoid valve allows fluid communication between the chamber and the reservoir by applying a flow direction to the fluid in the supply circuit. In the second position, the second solenoid valve allows fluid communication between the chamber and the reservoir by applying a fluid flow direction in the supply circuit opposite to that available in the first position. - Rest position, in which the second solenoid valve prevents fluid communication between the chamber and the reservoir.

5. The system according to claim 1, wherein, The solenoid valve is directly inserted into the path of the supply circuit.

6. The system according to claim 5, wherein, The solenoid valve has two actuation positions: -It allows fluid communication between the chamber and the reservoir by applying a fluid flow direction in the supply circuit opposite to the fluid flow direction available at the resting position, and -The location that prevents fluid communication between the chamber and the reservoir.

7. The system according to any one of claims 1-3, 5 and 6, wherein, The fluid is a liquid.

8. The system according to claim 4, wherein, The fluid is a liquid.

9. The system according to claim 7, wherein, The fluid is oil.

10. The system according to claim 8, wherein, The fluid is oil.

11. A method for controlling a system according to any one of the preceding claims, wherein: In order to raise the valve (12) and open the channel for melting material, the solenoid valve is energized. In order to lower the valve (12) and close the channel for melting material, the solenoid valve is de-energized, and In order to keep the valve (12) in the middle position, the solenoid valve is energized.

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