Motion control device with dual balance

Abstract

The invention relates to a motion control device with dual balance. Described is a device for controlling the movement of a load, comprising: a first conduit (10) designed to be connected to a first chamber (C1) of a hydraulic actuator (C); a second conduit (20) designed to be connected to a second chamber (C2) of the hydraulic actuator (C); a first balance valve (11) positioned along the first conduit (10), the first balance valve being normally closed and actuated towards an open position by pressure present in the second conduit (20); a second balance valve (21) positioned along the second conduit (20), the second balance valve being normally closed and controlled towards an open position by the pressure present in the first conduit (10); a third balance valve (13) positioned along the first conduit (10), the third balance valve being normally closed and actuated towards an open position by the pressure present in the second conduit (20).

Description

Technical Field

[0001] The present invention relates to an apparatus for controlling motion by balancing the load on each chamber of an actuator.

[0002] In more detail, the present invention relates particularly, if not exclusively, to a telescopic handler. Background Art

[0003] Prior art telehandlers consist of a vehicle providing a frame or "carriage" movable on wheels housing an operator's cab and a manipulator arm extendable to lift and lower a load.

[0004] In some models the manipulator arm is hinged directly to the carriage, while other models provide a platform or "turret" rotatably mounted on the carriage, with the cab and to which the manipulator arm is hinged.

[0005] Typically, the lifting system is driven by one or more hydraulic cylinders.

[0006] Each hydraulic cylinder can be supplied with a pressurized liquid, usually oil, from the base side or from the rod side. The supply from the base side combined with the discharge of the liquid on the rod side determines the outfeed movement of the rod and the lifting of the load. The supply from the rod side and / or the discharge of the liquid from the base side determines the retracting movement of the rod and the lowering of the load.

[0007] There is a control valve on the pipeline, which supplies the operating oil to the base side of the hydraulic cylinder. The purpose of the control valve is to allow the operating fluid to be freely supplied to the base side of the hydraulic cylinder if the rod out movement and the lifting of the load are to be determined, and to control or prevent the discharge of the operating fluid from the base side of the hydraulic cylinder if the rod re-entry and the lowering of the load are to be performed.

[0008] In particular, a control valve is a valve that is normally closed and is controlled by a control pressure during opening. In the absence of control pressure, the valve remains closed and prevents the discharge of operating fluid, thereby ensuring support of the load and preventing an uncontrolled lowering of the load. In the presence of control pressure, the valve opens in a controlled manner, thereby allowing the discharge of operating fluid and a subsequent controlled lowering of the load. In many cases, the control pressure is taken from a pipe that supplies operating oil to the rod side of the hydraulic cylinder.

[0009] The supply of operating fluid to the base side or the rod side of the hydraulic cylinder is usually established with the aid of a distributor, which has a center position, in which operating fluid is not supplied to the hydraulic cylinder, a first position, in which operating fluid is supplied to the base side of the hydraulic cylinder, while the rod side is connected to the discharge port, and a second position, in which operating fluid is supplied to the rod side of the hydraulic cylinder, while the base side is connected to the discharge port via a control valve.

[0010] In many cases, a central location of the distributor provides discharge to the connecting conduit to the base side of the hydraulic cylinder and to the connecting conduit to the rod side of the hydraulic cylinder.

[0011] The central position of the distributor is usually associated with a lack of control by the operator. In this case, the load must remain in the position it is in. In order for this to happen, and in particular so that the load is not lowered uncontrollably, the liquid present in the base side of the hydraulic cylinder must not be able to drain. The task of preventing the liquid from draining from the base side of the hydraulic cylinder is entrusted to a lowering control valve positioned along the connecting duct on the base side of the hydraulic cylinder. As mentioned above, the lowering control valve is normally closed, that is to say, it adopts the closed position in the absence of a lowering command. When in the closed position, the lowering control valve prevents the operating liquid from draining from the base side of the hydraulic cylinder, thus allowing the load to remain in a stationary position.

[0012] The current solution has a rather significant disadvantage, which is determined by the possibility that the descent control valve does not adopt the fully closed position but remains partially open, thereby allowing liquid to be discharged from the base side of the hydraulic cylinder. This occurs, for example, in the event of the presence of loose particles in the base side of the hydraulic cylinder due to machining.

[0013] Under these conditions, the load can experience uncontrolled and unexpected movement because it occurs without precise commands from the operator. Uncontrolled movement of the load is a hazardous event in itself. Summary of the invention

[0014] The object of the present invention is to provide a motion control device which overcomes the above-mentioned disadvantages.

[0015] A major advantage of the motion control device according to the invention is that it makes the risk of an uncontrolled drop of the load substantially negligible. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention illustrated by way of non-limiting example in the accompanying drawings, in which:

[0017] Figure 1a Schematically illustrates an embodiment of a motion control device according to the present invention;

[0018] Figure 1b Schematically shows Figure 1a variants of the implementation of;

[0019] Figure 2a A second embodiment of the motion control device according to the present invention is shown;

[0020] Figure 2b Schematically shows Figure 2a variants of the implementation of;

[0021] Figure 3a A third embodiment of the motion control device according to the present invention is shown;

[0022] Figure 3b Schematically shows Figure 3a A variation of the implementation scheme of . DETAILED DESCRIPTION

[0023] As already mentioned, the motion control device according to the invention is particularly useful on operator vehicles such as telehandlers or telescopic handlers.

[0024] Prior art telehandlers consist of a vehicle providing a frame or "carriage" movable on wheels housing an operator's cab and a manipulator arm extendable to lift and lower a load.

[0025] In some models the manipulator arm is hinged directly to the carriage, while other models provide a platform or "turret" rotatably mounted on the carriage, with the cab and to which the manipulator arm is hinged.

[0026] The hydraulic actuators are supplied by means of a control circuit comprising valves and distributors which direct the operating fluid to the various actuators according to specific activation commands, which may be automatic or given by an operator via suitable control elements.

[0027] In the following description, the term "balancing valve" refers to a device designed to control the flow out of an actuator by the movement of a gate, that is, an element movable in a valve seat between a closed position and at least one open position, in which it blocks the flow through the valve and the pipeline in which the valve is installed, and an open position in which it allows the flow through the valve and along the pipeline in which the valve is installed.

[0028] An open position or configuration indicating a valve is one in which the gate is in the open position.

[0029] The closed position or configuration of an indicating valve refers to the configuration in which the gate is in the closed position.

[0030] The command to open is the action of moving the gate toward the open position.

[0031] The command to close is the action of moving the gate toward the closed position.

[0032] The expression "hydraulic controlled valve" is used to denote a valve provided with at least a first control duct, that is to say a duct transmitting a first control pressure to a gate, which first control pressure pushes the gate towards an open position or a closed position. In the absence of action exerted by the control pressure, the elastic means act opposite to the thrust exerted by the control pressure to move the gate in the opposite direction. If the elastic means is positioned so that the gate moves towards the closed position, the valve will be defined as "normally closed".

[0033] In combination with or as an alternative to the elastic means, the valve may comprise a second control duct, that is to say a duct delivering a second control pressure to the gate, the second control pressure urging the gate in the opposite direction relative to the first control pressure.

[0034] In the following description, reference will be made to a hydraulic actuator in the form of a hydraulic cylinder (C) provided with a rod (S) which can slide in and out of the hydraulic cylinder (C) in an operating direction. However, the hydraulic actuator may be of a different type, for example it may be of a rotary type.

[0035] The hydraulic cylinder (C) is provided with a rod (S) which can slide in and out of the hydraulic cylinder (C) in the operating direction. The movement out of the rod is associated with the application of an active force, such as the lifting of a load. The reentry of the rod is associated with the release of an active force, such as the lowering of a load. In a known manner, the rod (S) is connected to a piston (Sp) which can slide in a sealed manner in the body of the hydraulic cylinder (C).

[0036] The piston (Sp) divides the inner chamber of the hydraulic cylinder into a first chamber (C1) and a second chamber (C2).

[0037] According to the embodiment shown, the first chamber (C1) is located on the base side of the hydraulic cylinder (C). The second chamber (C2) is located on the rod side of the hydraulic cylinder (C). Supplying the operating liquid to the first chamber (C1) and allowing the operating liquid to be discharged from the second chamber (C2) produces an increase in the volume of the first chamber at the expense of the second chamber, and determines the sliding out of the rod (S). Vice versa, supplying the operating liquid to the second chamber (C2) and allowing the operating liquid to be discharged from the first chamber (C1) produces an increase in the volume of the second chamber (C2) at the expense of the first chamber (C1), and determines the re-sliding in of the rod (S).

[0038] In the following description, reference will be made to the case where the resistance load on the hydraulic cylinder exerts an action tending to move the rod (S) inwards. Even if the resistance load on the hydraulic cylinder exerts an action tending to move the rod (S) outwards, or if the hydraulic cylinder (C) has two resistance loads, one exerting an action tending to move the rod (S) inwards and the other, on the contrary, exerting an action tending to move the rod (S) outwards, the solution according to the invention, suitably configured, can be used.

[0039] The control circuit of the hydraulic cylinder (C) includes a four-channel three-position distributor (D). The distributor (D) has a center position, a first position, and a second position. In the center position, the liquid is not delivered to the hydraulic cylinder; in the first position, the liquid is delivered to the first chamber (C1), and the second chamber (C2) is connected to the discharge port; in the second position, the liquid is delivered to the second chamber (C2) of the hydraulic cylinder, and the first chamber (C1) is connected to the discharge port.

[0040] according to Figure 1a , Figure 2a , Figure 3a In the embodiment shown in the figure, the central position of the distributor (D) connects both the first chamber (C1) and the second chamber (C2) to the discharge outlet in a so-called "Y" configuration, wherein the two connections to the chambers (C1, C2) converge to a single discharge outlet. The invention is particularly advantageous if the distributor (D) has a central position, wherein the two connections are connected by means of opposite outlets in a manner similar to that of the first chamber (C1) and the second chamber (C2). Figure 1b , Figure 2b , Figure 3b The so-called "H" configuration shown in FIG. 1 is connected to the discharge port.

[0041] The motion control device according to the invention comprises a first duct (10) designed to be connected to a first chamber (C1) of a hydraulic actuator (C).

[0042] The device also comprises a second duct (20) designed to be connected to a second chamber (C2) of the hydraulic actuator (C).

[0043] The first and second conduits (10, 20) are designed to also be connected to the distributor (D), that is, they are designed to connect the distributor (D) to the first chamber (C1) and the second chamber (C2), respectively.

[0044] A first balancing valve (11) is positioned along the first conduit (10). The first balancing valve (11) is normally closed and is actuated towards an open position by the pressure present in the second conduit (20).

[0045] A second balancing valve (21) is positioned along the second conduit (20). The second balancing valve (21) is normally closed and is controlled towards an open position by the pressure existing in the first conduit (10).

[0046] Each counter-balancing valve (11, 21) comprises a respective bypass (12, 22) configured for allowing a direct flow towards the hydraulic actuator (C) and for preventing a reverse flow.

[0047] The supply of operating liquid to the first or second conduit (10, 20) determines the filling and volume increase of the first or second chamber (C1, C2), respectively, while the volume of the other chamber decreases. In the case of a hydraulic cylinder (C), the supply of operating liquid to the first conduit (10) determines the volume increase of the first chamber (C1) and the volume decrease of the second chamber (C2), wherein the operating liquid is discharged from the latter.

[0048] The operating liquid supplied to the first pipe (10) passes through the bypass (12) of the first balancing valve (11) to the first chamber (C1). In practice, the latter is in the closed position. The discharge of the operating liquid from the second chamber (C2) takes place through the second balancing valve (20), which moves to the open position due to the effect of the pressure present in the first pipe (C1).

[0049] Similarly, the operating liquid supplied to the second pipe (20) passes through the bypass (21) of the second balancing valve (21) to the second chamber (C2). In fact, the latter is in the closed position. The discharge of the operating liquid from the first chamber (C1) occurs through the first balancing valve (10), which moves to the open position due to the effect of the pressure existing in the second pipe (C2).

[0050] According to the embodiment shown, the delivery of the operating liquid to the first chamber (C1) or the second chamber (C2) occurs by moving the dispenser (D) to the first position or the second position. Usually, the movement of the dispenser is performed by an operator using a special control unit known in the industry. The delivery of the operating liquid to the first chamber (C1) and the subsequent discharge of the liquid from the second chamber (C2) occur in response to a command for raising the load, which causes the dispenser (D) to move to the first position. The delivery of the operating liquid to the second chamber (C2) and the subsequent discharge of the liquid from the first chamber (C1) occur in response to a command for lowering the load, which causes the dispenser (D) to move to the second position.

[0051] In the absence of a controller, the distributor (D) moves to a central position in which none of the chambers (C1, C2) is supplied with operating liquid. According to the embodiment shown, the central position of the distributor (D) connects both the first duct (10) and the second duct (20) to the discharge.

[0052] Advantageously, the device according to the invention comprises a third balancing valve (13) positioned along the first conduit (10), the third balancing valve being normally closed and being actuated towards an open position by the pressure present in the second conduit (20). The third balancing valve (13) is positioned along the first conduit (10) in series with respect to the first balancing valve (11).

[0053] The third counter-balance valve (13) further comprises a bypass (14) configured to allow a direct flow towards the hydraulic actuator (C) and prevent a reverse flow.

[0054] The third balancing valve (13) is operated in a substantially simultaneous manner with the first balancing valve (11). In practice, supplying the operating liquid to the second conduit (20) and determining the opening of the first balancing valve (11) also determines the opening of the third balancing valve (13) to allow the operating liquid to be discharged from the first chamber (C1).

[0055] The third counterbalance valve (13) provides an extremely important safety advantage for the control device according to the invention.

[0056] In fact, under low pressure conditions in the second pipe (20), the first and third balancing valves (11, 13) move to the closed position, blocking the first pipe (10) and preventing the discharge of the operating liquid from the first chamber (C1). In the event of a malfunction of one of the two valves (11, 13), for example if one of the two valves is not completely closed, the other valve is able to ensure the closing of the first pipe (10) in any case.

[0057] In the case where the first pipe (10) is connected to a chamber of a hydraulic actuator designed to lift and support a load, the use of two counter-balance valves (11, 13) along the first pipe (10) is particularly advantageous in terms of safety. According to the embodiment shown, the chamber used to lift and support the load is the first chamber (C1), that is to say the chamber which increases its volume after the supply of operating liquid, determining the outward movement of the rod (S). In fact, in this case, the hydraulic actuator must remain at rest without any command from the operator, guaranteeing stable maintenance of the load. For this reason, the first chamber (C1) cannot be emptied through the first pipe (10), and therefore the first pipe (10) must remain closed. The two counter-balance valves (11, 13) positioned along the first pipe move to the closed position without a command and under low pressure conditions in the second pipe (20), providing a substantially certain guarantee for the closing of the first pipe (10). This is even more important if the distributor (D) has an open center, as in the embodiment shown, that is, if the distributor (D) connects both the first duct (10) and the second duct (20) to the discharge opening in a central position.

[0058] According to the preferred but not exclusive embodiment shown, the motion control device according to the present invention comprises a first control conduit (p1) which connects the first balancing valve (11) and the second conduit (20). In addition, the motion control device comprises a second control conduit (p2) which connects the second balancing valve (12) and the first conduit (10). The third control conduit (p3) is designed to connect the third balancing valve (13) and the second conduit (20).

[0059] The operation of the motion control device according to the present invention is performed in the following mode.

[0060] In the presence of a command for raising or lifting the load, the distributor (D) moves to a first position, connecting the first duct (10) with a source of pressurized operating liquid (e.g. a pump). The operating liquid passes along the first duct (10) through the bypass (12, 14) to the first chamber (C1). At the same time, following the thrust exerted by the piston (Sp), the operating liquid present in the second chamber (C2) is discharged through the second duct (20). The flow discharged along the second duct (20) is allowed by opening the second balancing valve (21), which adopts an open position due to the pressure present in the first duct (10). The pressure present in the first duct (10) is transmitted to the second balancing valve (21) via the second control duct (p2).

[0061] In the presence of a command for lowering the load, the distributor (D) moves to the second position, connecting the second duct (20) to a source of pressurized operating liquid (e.g. a pump) and connecting the first duct (10) to a discharge port. The operating liquid passes along the second duct (20) through the bypass (22) to the second chamber (C2). At the same time, following the thrust exerted by the piston (Sp), the operating liquid present in the first chamber (C1) is discharged through the first duct (10). The flow along the first duct (10) is allowed to be discharged by opening the first balancing valve (11) and the third balancing valve (13). Due to the pressure present in the second duct (20), the two valves (11, 13) adopt an open position in a substantially simultaneous manner. The pressure present in the second duct (20) is transmitted to the first balancing valve (11) via the first control duct (p1) and to the third balancing valve (13) via the third control duct (p3).

[0062] If there is no control, the distributor (D) moves to the center position. In this condition, the first and second conduits (10, 20) are connected to the discharge and are therefore at low pressure, and the balancing valves (11, 12, 13) are all moved to the closed position.

[0063] According to the embodiment shown, the third control conduit (p3) is connected to the first control conduit (p1) and the third balancing valve (13). In other words, the third control conduit (p3) is a branch of the first control conduit (p1). In some cases, this configuration simplifies the construction of the motion control device according to the present invention.

[0064] Preferably, but not necessarily, each balancing valve (11, 12, 13) has a chamber for accommodating a closing spring, which is positioned to communicate with the outlet of the valve. According to other embodiments not shown, the chamber for accommodating the spring communicates with a low pressure environment. For example, the chamber can be ventilated in air.

[0065] Advantageously, but not necessarily, the third balancing valve (13) is provided with an auxiliary conduit (131) which connects the chamber for accommodating the spring with an extension of the first conduit (10) between the distributor (D) and the first balancing valve (11). This allows the first and third balancing valves (11, 13) to react in a manner equal to the control pressure from the first and third control conduits (p1, p3). In this way, the first and third balancing valves (11, 13) can be calibrated to the same opening pressure.

[0066] The above solution relates to the situation where the resistive load on the hydraulic cylinder applies an action tending to move the rod (S) inwards.

[0067] In the case where the resistive load on the hydraulic cylinder applies an action tending to move the rod (S) outward, the first conduit (10) is connected to the second chamber (C2) and the second conduit (20) is connected to the first chamber (C1), as Figure 2a as shown in .

[0068] Figure 3a A situation is shown in which the hydraulic cylinder (C) has two resistive loads, one exerting an action tending to move the rod (S) inwards and the other, on the contrary, exerting an action tending to move the rod (S) outwards. In this case, the device according to the invention comprises a fourth counterbalance valve (24) positioned along the second duct (20), which is normally closed and actuated towards an open position by the pressure present in the first duct (10).

[0069] The fourth balancing valve (24) is positioned along the second conduit (20) in series with respect to the second balancing valve (21).

[0070] The fourth counter-balancing valve (24) further comprises a bypass (25) configured to allow direct flow towards the hydraulic actuator (C) and prevent reverse flow.

[0071] The fourth balancing valve (24) operates in a substantially simultaneous manner with the second balancing valve (21). In practice, supplying the operating liquid to the first conduit (10) determines the opening of the second balancing valve (21) and also the opening of the fourth balancing valve (24) to allow the operating liquid to be discharged from the second chamber (C2).

[0072] The fourth control conduit (p4) is designed to connect the fourth balancing valve (24) and the first conduit (10). According to the embodiment shown, the fourth control conduit (p4) is connected to the second control conduit (p2) and the fourth balancing valve (24). In other words, the fourth control conduit (p4) is a branch of the second control conduit (p2). In some cases, this configuration simplifies the construction of the motion control device according to the present invention.

[0073] The advantages provided by the fourth balancing valve (24) are substantially the same as those already described with respect to the third balancing valve (13), but relate to any failure of the second control conduit (20) and the second balancing valve (21).

[0074] Advantageously, but not necessarily, the fourth counterbalance valve (24) is provided with an auxiliary conduit (241) which connects the chamber for accommodating the spring with an extension of the second conduit (20) between the distributor (D) and the second counterbalance valve (21). This allows the second and fourth counterbalance valves (21, 24) to react in a manner equal to the control pressure from the first and third control conduits (p2, p4). In this way, the first and third counterbalance valves (21, 24) can be calibrated to the same opening pressure.

[0075] Advantageously, one or more of the balancing valves (11, 12, 21, 24) can be provided with a state detector designed to emit a signal indicating the opening state of the corresponding valve. The state detection is particularly useful for the third balancing valve (13) and for the fourth balancing valve (24) (if present) to indicate an unplanned and uncontrolled opening condition, indicating the presence of a fault or impurities in the circuit. The same advantages can obviously be obtained for the other balancing valves.

[0076] According to a possible embodiment not shown in detail, the detection of the state of the balancing valve comprises one or more sensors. For example, sensors that can be used include LVDT type linear motion sensors designed to detect the movement and / or position of the gate of the balancing valve. In addition, the state detection can be provided with one or more pressure sensors designed to measure the pressure in the pipeline to control the balancing valve.

[0077] The status detection may be associated with a control unit provided with a monitoring algorithm configured to detect any fault in which a balancing valve has an unclosed position despite no control and to signal any fault, for example to a display.

Claims

1. A device for controlling the movement of a load, comprising: A first conduit (10) designed to be connected to a first chamber (C1) of a hydraulic actuator (C); A second conduit (20) designed to be connected to a second chamber (C2) of the hydraulic actuator (C); a first balancing valve (11) positioned along the first conduit (10), the first balancing valve being normally closed and being actuated towards an open position by the pressure existing in the second conduit (20); a second balancing valve (12) positioned along the second conduit (20), the second balancing valve being normally closed and controlled towards an open position by the pressure existing in the first conduit (10); Characterized in that the device comprises a third balancing valve (13) positioned along the first duct (10), the third balancing valve being normally closed and being actuated towards an open position by the pressure existing in the second duct (20).

2. The device according to claim 1, comprising: A first control pipeline (p1) for communicating the first balancing valve (11) with the second pipeline (20); a second control pipeline (p2), connecting the second balancing valve (12) and the first pipeline (10); The third control pipeline (p3) enables the third balancing valve (13) and the second pipeline (20) to communicate with each other.

3. The device according to claim 2, wherein: The third control pipeline (p3) is connected to the first control pipeline (p1) and the third balancing valve (13).

4. The device according to any one of the preceding claims, wherein: Each counter-balancing valve (11, 12, 13) comprises a respective bypass (12, 22, 14) configured for allowing a direct flow towards the hydraulic actuator (C) and for preventing a reverse flow.

5. The device according to any one of the preceding claims, comprising a four-channel three-position distributor (D) connected to the first pipe (10) and the second pipe (20), the four-channel three-position distributor being configured to adopt a center position, a first position and a second position, in which the operating liquid is not supplied to the first pipe (10) and the second pipe (20); in the first position, the operating liquid is supplied to the first pipe (10), and the second pipe (20) is connected to a discharge port; in the second position, the operating liquid is supplied to the second pipe (20), and the first pipe (10) is connected to the discharge port.

6. The device according to claim 5, wherein: The four-way three-position distributor (D) is configured such that at the center position, the first pipe (10) and the second pipe (20) are connected to the discharge port.

7. The device according to any of the preceding claims, comprising a fourth balancing valve (24) positioned along the second duct (20), the fourth balancing valve being normally closed and actuated towards an open position by the pressure existing in the first duct (10).

8. The device according to claim 7, comprising a fourth control duct (p4) designed to connect the fourth balancing valve (24) to the first duct (10).

9. The device according to claim 7, wherein: The fourth counter-balance valve (24) includes a bypass (25) configured to allow direct flow toward the hydraulic actuator (C) and prevent reverse flow.

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