ANTI-RUPTURE TUBE DEVICE

Abstract

 A hydraulic tube rupture protection device is disclosed that ensures safety conditions in the event of rupture of a flexible tube connected to a hydraulic actuator of an arm of an excavator, in which the tube rupture protection device comprises a control valve controlled by a pilot line connected to a control member that is manoeuvrable by an operator, a logic element is arranged on a connecting line that connects the pilot line to the flexible tube; in the event of rupture of the flexible tube, without moving the control member, the logic element will open at least partially, causing the at least partial closure of the control valve, limiting the descent speed of the arm of the excavator.

Description

Background of the invention

[0001] The invention relates to a tube rupture protection device, in particular a hydraulic protection device that ensures safe conditions in the case of rupture of a (flexible) tube connected to a hydraulic actuator.

[0002] Specifically, but not exclusively, the invention can be applied to the control system of a working machine (for example an excavating and/or load handling machine), in which the drive can be provided by a linear (cylindrical) hydraulic actuator, to ensure the safe descent control in the event of rupture of the flexible tube connected to the bottom of the linear actuator.

[0003] The prior art comprises various types of tube rupture valves that protect against the rupture of the flexible tube that in an excavator, connects the bottom of the hydraulic cylinder to the distributor. In general, the tube rupture valves are installed directly on the cylinder without the interposition of the flexible tube. Standard ISO 8643 requires, in the event of rupture of the flexible tube during lowering of the lifting arm, the arm not to be able to exceed twice the speed at the moment of rupture, with the control lever (joystick) maintained in the same position.

[0004] According to a first type, the prior art tube rupture valves are piloted by a first pressure on the stem side of the hydraulic cylinder and by a second pressure on the bottom side. The tube rupture protection device in question does not belong to these types of valves, which are particularly complex.

[0005] The tube rupture protection device in question belongs to a second type of tube rupture valve - simpler than the preceding types - which normally stay closed and are piloted in opening by a pilot pressure taken from the same pilot line that pilots the distributor of the operating fluid of the cylinder, at the command of the same control lever (joystick) that is manoeuvred by the operator and also pilots the shuttle of the distributor.

[0006] In the event of rupture of the tube, the tube rupture valves have to be configured in such a manner as to generate an appropriate pressure drop. However, the tube rupture valves of known type can generate pressure drops that are relatively high, with a consequent risk of slowing the machine also during normal operation, together with a possible increase in energy consumption and/or operating temperature. Further, the prior art rupture valves normally require a specific setting for each machine and/or for each modification of the configuration of the machine. Consider, for example, adding a device (for example a lifting fork) that modifies the features of the machine during the descent of the arm, so that the valve might not ensure the requested requirements.

[0007] GB 2 514 112 A, JP 4 890147 B2 and JP 2014 206245 A show a tube rupture protection device as in the preamble of claim 1.

Summary of the invention

[0008] One object of the invention is to make a tube rupture protection device that is able to overcome the aforesaid limits and drawbacks of the prior art.

[0009] One object of the invention is to provide a tube rupture protection device for the safe descent control in the event of rupture of the flexible tube.

[0010] One advantage is to ensure that, in the case of a tube rupture, the descent speed of the working arm of a machine (excavator) does not exceed a set value (for example twice the speed preceding the rupture).

[0011] One advantage is to provide a tube rupture protection device that, during normal operations, generates a relatively reduced pressure drop.

[0012] One advantage is to make available a tube rupture protection device with great versatility, that is for example able to adapt to different types of machine and/or to various configurations of a machine, without the need to carry out a specific setting as the machine and/or the configuration thereof changes.

[0013] One advantage is to give rise to a tube rupture protection device that is constructionally simple and cheap.

[0014] One advantage is excellent controllability of the movable arm of a working machine ensuring great stability during movement of the arm.

[0015] One advantage is to ensure good manoeuvrability and optimum comfort for the operator during the various material handling operations.

[0016] One advantage is to reduce energy consumption, obtaining high energy efficiency during the step of controlling the movable arm.

[0017] One advantage is to provide a device with a mechanical seal with virtually no leaking in the joining zone between the movable element (piston) and the seat thereof, which is able to offset the leak that is normally present in the distributor (typically consisting of a shuttle distributor).

[0018] Such objects and advantages, and still others, are achieved by the tube rupture protection device according to one or more of the claims set out below.

[0019] In one embodiment, a hydraulic tube rupture protection device, which is in particular suitable for controlling (limiting) the descent speed in the case of rupture of a tube connected to a hydraulic actuator of a movable arm of a working machine, comprises a control valve (of the pressure and/or of the flow) arranged on a hydraulic line connected to the tube; the control valve is controlled by a pilot line connected to a control member (joystick) that is manoeuvrable by an operator and also controls the valve (distributor) that adjusts the flow of operating fluid with respect to the hydraulic actuator; the tube rupture protection device comprises at least one hydraulic element (for example a logic element, a pressure limiting valve, a check valve, etc) arranged on a connection line that connects the pilot line to the hydraulic line connected to the tube, whereby, in the event of rupture of the tube and even without moving the control member, the hydraulic element will open at least partially the connection line, causing the at least partial closure of the control valve, thus limiting the descent speed of the movable arm.

Brief description of the drawings

[0020] The invention can be better understood and implemented with reference to the attached drawings that illustrate embodiments by way of non-limiting examples, in which:

Figure 1 shows a diagram of a circuit that includes a first embodiment of a tube rupture protection device according to the invention;

Figure 2 shows a diagram of a circuit that includes a second embodiment of a tube rupture protection device according to the invention;

Figure 3 shows a diagram of a circuit that includes a third embodiment of a tube rupture protection device according to the invention;

Figure 4 shows a diagram of a circuit that includes a fourth embodiment of a tube rupture protection device according to the invention;

Figure 5 shows a diagram of a circuit that includes a fifth embodiment of a tube rupture protection device according to the invention;

Figure 6 shows a diagram of a circuit that includes a sixth embodiment of a tube rupture protection device according to the invention;

Figure 7 shows some embodiments of hydraulic elements that can be arranged in a tube rupture protection device according to the invention on the connection line 4 that connects the pilot line 3 to the tube T;

Figure 8 shows a partial section of the fifth embodiment of the tube rupture protection device schematised in Figure 5;

Figure 9 shows a diagram of a circuit that includes a seventh embodiment of a tube rupture protection device according to the invention.

Detailed description

[0021] With reference to the aforesaid figures, for greater clarity, analogous elements of different embodiments have been indicated by the same numbering.

[0022] With 1, a tube rupture protection device has been indicated that is suitable for use, in particular, on a working machine (for example an excavating and/or load handling machine). The tube rupture protection device 1 is used, in particular, to limit the descent speed of a movable arm in the event of rupture of the (flexible) tube that, normally, connects the directional control valve (distributor) to the hydraulic actuator that controls movement of the arm of the working machine. The tube rupture protection device 1 may comprise, in particular, a valve unit made as a single block (schematized with a dashed line in Figures 1-6 and 9).

[0023] The tube rupture protection device 1 may comprise, in particular, a hydraulic line 2 in turn comprising a first port P1 intended for the connection with a (linear) hydraulic actuator C and a second port P2 intended for the connection with a (flexible) tube T at risk of rupture. The tube T may be, in turn, connected to a directional control valve D of the operating fluid of the actuator C. The directional control valve D may be, in particular, of proportional type.

[0024] The tube rupture protection device 1 may comprise, in particular, at least one control valve V operating in the hydraulic line 2. The control valve V may comprise, in particular, a control valve (of the pressure and/or of the flow) of known type that can normally be used in a tube rupture protection device. The control valve V may comprise, for example, a control valve (of the pressure and/or of the flow) with a control of proportional type.

[0025] The control valve V may comprise, in particular, a valve of mechanical seal type, i.e. a valve configured for ensuring a mechanical seal with virtually no leaking, for example by using specific mechanical components (that are in themselves known), such as a movable element (piston) and a seat for the movable element with no leaking.

[0026] The control valve V may comprise, in particular, at least one first (ascent) position in which it permits a flow towards the first port P1 and prevents a flow towards the second port P2. The control valve V may comprise, in particular, at least one second (descent) position in which it permits a flow to the second port P2, for example with a localized load loss (of a preset amount).

[0027] In other embodiments, which are not illustrated the control valve V may comprise other types of valve (also of known type).

[0028] The tube rupture protection device 1 may comprise, in particular, a pilot line 3 arranged for piloting the control valve V to the aforesaid first position. The pilot line 3 may comprise, as in these embodiments, a third port P3 intended for the connection with a control device J manoeuvrable by an operator. The control device J (for example a joystick of known type) may be configured, as in these embodiments, so as to control simultaneously both the directional control valve D and the control valve V.

[0029] The tube rupture protection device 1 may comprise, in particular, a connection line 4 arranged for connecting the pilot line 3 to a portion of the hydraulic line 2 comprised between the second port P2 and the control valve V.

[0030] The tube rupture protection device 1 may comprise, in particular, at least one circuit element 5, or hydraulic element, arranged in the connection line 4. The circuit element 5 is configured so as to be closed in the normal operating steps and to be opened automatically (at least partially) in the case of a tube rupture (because of a pressure drop that will occur in the aforesaid portion of the hydraulic line 2 comprised between the second port P2 and the control valve V).

[0031] This circuit element 5 may be, in particular, sensitive to a pressure present in the aforesaid portion of the hydraulic line 2 such as to close the connection line 4 when in the aforesaid portion of the hydraulic line 2 there is a first pressure in the case of an intact tube T, i.e. in a normal operating situation.

[0032] This circuit element 5 may be, in particular, sensitive to a pressure present in the aforesaid portion of the hydraulic line 2 so as to open (at least partially) the connection line 4 when in the aforesaid portion of the hydraulic line 2 there is a second pressure lower than the aforesaid first pressure. The second pressure may be due, in particular, to rupture of the tube T, i.e. in an emergency situation that requires an automatic and immediate intervention to maintain the system in a safe condition, even if the operator does not promptly return the control device J to the safety position.

[0033] This circuit element 5 may comprise, for example, at least one of the circuit elements illustrated in Figure 7 and indicated from A to F. In Figures 7A to 7F, with I the side of the circuit element 5 to the control device J has been indicated, with II the side towards the tube T, with III the side (if present) towards the drain R.

[0034] The circuit element 5 may comprise, as in the embodiments in Figure 1 and Figure 6, a pressure control valve, for example the valve in Figure 7A. The circuit element 5 may comprise, in other embodiments which are not illustrated, a pressure control valve as in Figure 7B or as in Figure 7D. The circuit element 5 could comprise, in particular, a proportional control valve, as in the embodiments in Figures 7A and 7D. The circuit element 5 could comprise other embodiments of maximum pressure valves (of known type).

[0035] The circuit element 5 may comprise, in other embodiments which are not illustrated, the check valve in Figure 7C arranged so as to permit a flow from the pilot line 3 to the hydraulic line 2 (connected to the flexible tube T).

[0036] The circuit element 5 may comprise, as in the embodiments in Figures 2, 3, 4 and 5, a logic element, for example like that of Figure 7E or 7F, which can be arranged in such a manner as to be piloted in closure by the pressure in the aforesaid portion of the hydraulic line 2. The logic element may be piloted in closure by elastic means. The logic element may be piloted in opening by the pressure coming from the control device J (with the possible interposition of first choking means C1 and/or second choking means C2).

[0037] The logic element may be configured, in particular as in Figure 7E, in such a manner as to have a differential area dimensioned for maintaining the element in balance when the pressure on the side of the hydraulic line 2 (tube side) is (significantly) lower than the pressure on the opposite side (joystick side), for example with a ratio greater than 1:3, or 1:4, or 1:5, and less than 1:12, or 1:10, or 1:8 (for example 1:6, in particular 1 bar on one side and 6 bar on the opposite side).

[0038] The logic element may be configured, in particular as in Figure 7F, in such a manner as to have a differential area dimensioned for maintaining the element in balance when the pressure on the side of the hydraulic line 2 (tube side) is (significantly) greater than the pressure on the opposite side (joystick side), for example with a ratio greater than 3:1, or 4:1, or 5:1, and less than 12:1, or 10:1, or 8:1 (for example 6:1, in particular 6 bar on one side and 1 bar on the opposite side).

[0039] In all the embodiments disclosed above, the circuit element 5 facilitates closing of the control valve V during the emergency due to the rupture of the tube T, causing a desired reduction in descent speed, in a controlled manner, further limiting dispersal of the operating fluid that exits through the rupture of the tube T. It is possible, in particular, to reach complete closure of the control valve V, gradually, i.e. without the risk of generating instability in the movement of the movable arm controlled by the hydraulic actuator C.

[0040] In other words, the arrangement of the connection line 4 and of the circuit element 5 sensitive to the pressure (in particular, together with first choking means C1 and/or with second choking means C2, as will be explained better further on in the description), enables the valve V to generate a relatively low load loss during normal operation, to then generate automatically (gradually) a greater load loss immediately after the rupture of the tube, so that the valve V is able to close, also only partially, because of the rupture of the tube, without the need to intervene on the control device J.

[0041] The protection device 1 may comprise, as in the embodiments in Figures 3, 4, 5 and 9, a locking valve 7 arranged for blocking a signal (for example present on the connection line 4 and coming from the hydraulic line 2) directed to the control valve V. The locking valve 7 may be piloted, in particular, by a pressure coming from the pilot line 3. The locking valve 7 may be positioned, in particular, on the connection line 4. The locking valve 7 may be positioned between the control device J and the circuit element 5. The locking valve 7 may be positioned between the circuit element 5 and the hydraulic line 2.

[0042] The locking valve 7 may comprise a valve with at least two positions, in the specific embodiments of Figure 3, 5 and 9 with three positions, with at least one central open position and at least two lateral, or external, or end closing positions, opposite one another with respect to the central open position. A first lateral closing position could be piloted, for example, by elastic means. A second first lateral closing position could be piloted, for example, by a pressure taken by a pilot line 9 and coming from the pilot line 3. In other embodiments, like that of Figure 4, the locking valve 7 could comprise a two position valve with an open position (piloted by a pressure taken by a pilot line 9) and a closed position (piloted by elastic means).

[0043] The locking valve 7 may be configured, in particular, so as to remain closed (for example in the first lateral closing position) for a pressure lower than a first value (where the first value may be, in particular, the same as the opening operating pressure of the circuit element 5, for example equal to 5 bar). The locking valve 7 may be configured, in particular, in such a manner as to be open (for example in the first central open position) when the pressure is comprised between the aforesaid first value and a second value (where the second value may be, in particular, the pressure beyond which it is no longer necessary to activate the tube rupture protection device 1, for example a 12 bar value). The locking valve 7 may be configured, in particular, in such a manner as to be closed (for example in the second first lateral closing position) for a pressure greater than the aforesaid second value, i.e. when the tube rupture protection device 1 can be deactivated.

[0044] When the locking valve 7 comprises a two position valve (Figure 4) with an open position and a closed position it is possible for the locking valve 7 to be configured, in particular, so as to remain closed for a pressure lower than the first value and in such a manner as to be open when the pressure is greater than the first value.

[0045] The embodiment of Figure 8 shows (partially) a tube rupture protection device 1, the hydraulic diagram of which corresponds to that of Figure 5, in which the (three-position) locking valve 7 is integrated into a movable element (piston) of the valve V.

[0046] The tube rupture protection device 1 may comprise, in particular, first choking means C1 (for example at least one adjustable grubscrew) arranged in the pilot line 3. The first choking means C1 may be arranged, in particular, between the third port P3 and the connection line 4.

[0047] The first choking means C1 may comprise, in particular, a calibrated orifice with a determined diameter.

[0048] The tube rupture protection device 1 may comprise, in particular, second choking means C2 (for example at least one adjustable grubscrew) arranged in the connection line 4. The second choking means C2 may be arranged, in particular, between the circuit element 5 and the pilot line 3.

[0049] The second choking means C2 may comprise, in particular, a calibrated orifice with a determined diameter.

[0050] The first choking means C1 and the second choking means C2 may be calibrated in such a manner as to obtain a desired limitation of the descent speed of the movable arm connected to the hydraulic actuator C in the case of a tube rupture.

[0051] It is possible, in fact, by suitable sizing of the two choking means C1 and C2, to obtain a desired reduction of the descent speed of the arm. For example, to obtain a 50% reduction, the first choking means C1 and the second choking means C2 may comprise two calibrated orifices with the same diameter (for example 1 mm). For example, to obtain a speed reduction of less than 50%, the first choking means C1 will have a passage section that is greater than the second choking means C2. For example, to obtain a speed reduction that is greater than 50%, the first choking means C1 will have a passage section that is less than the second choking means C2.

[0052] The tube rupture protection device 1 may comprise, in particular, an auxiliary drainage line 8 arranged for draining the above circuit element 5. The tube rupture protection device 1 may comprise, in particular, a fourth port P4 connected to the aforesaid auxiliary drainage line 8. The fourth port P4 may be intended, as in this embodiment, for connection with a drain R.

[0053] The control circuit of the hydraulic actuator C may comprise, in particular, the aforesaid directional control valve D arranged for distributing in a controlled manner the operating fluid of the actuator C. The control circuit may comprise, in particular, the flexible tube T at risk of rupture arranged for connecting the directional control valve D with the hydraulic actuator C. The control circuit may comprise, in particular, the tube rupture protection device 1 arranged between the flexible tube T and the hydraulic actuator C. The control circuit may comprise, in particular, the control device J manoeuvrable by an operator. The control device J may be configured and arranged so as to control simultaneously both the directional control valve D and the control valve V.

[0054] With reference to Figure 8, with B a valve body of the tube rupture protection device 1 has been indicated and with S a cursor that is movable axially within the valve body B. The cursor S may comprise, in particular, the piloting piston of the valve V. With reference to Figure 8, to the right of the cursor S (piloting piston) the piloting pressure is present, whereas on the left there is the main movable shutter means of the valve V (for example of known type).

[0055] In Figure 8, moreover, with 10 a drain obtained in the cursor S for bleeding the air from inside the device 1, with 11 a connecting recess that is obtained on the outer surface of the cursor S for selective connecting to various zones of the valve body B according to the position of the cursor S, with 12 a space inside the circuit element 5 and connected to the second port P2, have been indicated.

[0056] The cursor S is a movable element that gives rise, in cooperation with one or more recesses on the valve body B, to the (three-position) locking valve 7. With S1, S2, S3 and S4 some significant strokes have been indicated that the cursor S can execute with reference to the position of the connection recess 11.

[0057] In particular, with S1 an initial stroke has been indicated, starting from an end position in which the valve is closed. The stroke S1 comprises, substantially, a dead stroke that is used to eliminate possible clearance of at least one movable element (piston unit) of the valve V that operates on the cursor S. At the end of the stroke S1, the locking valve 7 may be closed. At the end of the stroke S1, the recess 11 may still be in a covering position with respect to the hole communicating with the connection line 4. At the end of the stroke S1 the control valve V may be in a pre-opening step whilst the locking valve 7 may still be closed. During the stroke S1, in particular, drainage (of some drops of the) operating fluid may occur so as to generate depressurization in the actuator C.

[0058] In particular, with S2 an effective pre-opening stroke of the control valve V has been indicated, whereas the locking valve 7 may still be closed. In this step draining may be achieved, in particular, from the control valve V, of (some drops of the) operating fluid that is suitable for generating depressurization in the actuator C. During the stroke S2 the piloting pressure may act, in particular, both on the control valve V and on the directional control valve D, causing a first flow indication thereof, but with a movement of the actuator C that can still be imperceptible.

[0059] At the end of the pre-opening stroke S2 and at the start of an opening stroke S3 it is possible to reach an opening pressure of the control valve V, that may be, for example, about 5 bar; in this step also the locking valve 7 may start to open, so the connection recess 11 no longer has a cover of the hole that communicates with the connection line 4 and the fluid can start to transit.

[0060] In particular, in the opening stroke S3 true opening of the locking valve 7 occurs, to an actual use position. During the stroke S3, it is possible to reach a pressure comprised between the opening pressure (5 bar) and a (preset) limit pressure greater than the opening pressure (for example, as said previously, a limit pressure of 12 bar). This is the step in which the tube rupture protection device in Figure 8 mainly performs the action of limiting the descent speed, ensuring safe conditions in the case of a tube rupture.

[0061] Substantially, in the pre-opening stroke S2 the control valve V may have a pre-opening, whereas the locking valve 7 may remain closed and in the opening stroke S3 both the valves V and 7 may have a true opening.

[0062] In particular, with S4 a (possible) end stroke has been indicated in which the locking valve 7 is reclosed again. The end stroke S4 may be provided, depending on the needs and the requests of the user of the tube rupture protection device, in particular if it is desirable to limit the descent speed whatever the speed or only for a given descent speed range.

[0063] The tube rupture protection device 1 may comprise, as in the embodiments in Figures 5, 6 and 9, anti-collision means that may comprise, in particular, a maximum pressure valve 13 arranged on a drainage line 14 that connects the actuator C with the piloting of the valve V. The drainage line 14 may be connected, for example, to the pilot line 3, in particular by a selector valve 6 that selects, between the two aforesaid lines, the line with greater pressure, automatically excluding the other. The drainage line 14 may be connected to the drain R, for example by a drainage line 15 that branches off from the drainage line 14 to reach the drainage line 8. On the drainage line 15 it is possible to arrange third choking means C3 (a calibrated orifice). The fluid discharged from the maximum pressure valve 13, through the third choking means C3, may generate, in particular, an increase in pressure that spreads in the pilot line 3 and thus on the piloting piston, thus opening the control valve V and releasing the fluid from the actuator C to reduce the pressure thereof. The anti-collision means may be arranged, in particular, to protect the hydraulic system from pressure peaks or overloads.

[0064] In Figure 9 another embodiment of the tube rupture protection device is shown that comprises the hydraulic line 2, the first port P1, the second port P2, the control valve V, the pilot line 3, the third port P3, the connection line 4, the circuit element 5, the (three-position) locking valve 7, the first choking means C1, the second choking means C2, the auxiliary drainage line 8 (arranged in particular for draining the control valve V), the fourth port P4 to be connected to a drain, the anti-collision means comprising the maximum pressure valve 13, the drainage line 14, the selector valve 6, the drainage line 15, the third choking means C3. In the specific embodiment of Figure 9, the (three-position) locking valve 7 is integrated into the movable element of the control valve V.

[0065] The second choking means C2 may be, in particular (as in this embodiment), integrated into the movable element of the control valve V. The second choking means C2 may be arranged, according to other embodiments which are not illustrated, between the locking valve 7 (in this case with three positions) and the circuit element 5. The second choking means C2 may be arranged, according to other embodiments which are not illustrated, between the circuit element 5 and the hydraulic line 2.

[0066] The auxiliary drainage line 8 may be, in particular (as in this embodiment), arranged for draining the control valve V.

[0067] The tube rupture protection device may comprise, in particular (as in this embodiment in Figure 9), a bypass valve 16 arranged on a bypass line 17 to bypass the control valve V along the hydraulic line 2 in a direction of the flow that goes from the second port P2 to the first port P1. The bypass system (valve 16 and line 17) is used, in particular, in the ascent step to bypass the descent control valve V that does not work during the ascent.

[0068] The tube rupture protection device may comprise, in particular (as in this embodiment of Figure 9), an equalizing line 18 that connects the first port P1 to an equalizing port E. The equalizing system (line 18 and port E) is used, in particular, if the working machine comprises two or more parallel cylinders (excavator type) and is thus provided with two or more tube rupture protection devices, one for each cylinder. In this situation, it is possible to connect together the equalization ports of the various safety devices (for example by a tube), in order to balance the pressures inside the various cylinders, so that such pressures are similar, to prevent one cylinder bearing the load and another cylinder not bearing the load.

[0069] In all the embodiments disclosed above, in the event of rupture of the tube T and even without moving the control member J, the circuit element 5, or hydraulic element will open at least partially the connection line 4, causing the at least partial closure of the control valve V, limiting the descent speed of the actuator C.

Claims

1. Hydraulic tube rupture protection device (1), comprising:

- a hydraulic line (2) comprising a first port (P1) intended for the connection with a hydraulic actuator (C) and a second port (P2) intended for the connection with a tube (T) at risk of rupture;

- at least one control valve (V) operating in said hydraulic line (2), said control valve (V) comprising at least one first position in which it allows a flow towards said first port (P1) and prevents a flow towards said second port (P2) and at least one second position in which it permits a flow towards said second port (P2);

- a pilot line (3) arranged to pilot said control valve (V) towards said first position, said pilot line (3) comprising a third port (P3) intended for the connection with a control device (J) which is manoeuvrable by an operator;

- a connection line (4) arranged to connect said pilot line (3) with a portion of said hydraulic line (2) between said second port (P2) and said at least one control valve (V);

- at least one circuit element (5) arranged in said connection line (4) and sensitive to a pressure present in said portion of said hydraulic line (2) to close said connection line (4) when in said portion of said hydraulic line (2) there is a first pressure, in case of intact tube (T), and to open at least partially said connection line (4) when in said portion of said hydraulic line (2) there is a second pressure, lower than said first pressure, in case of broken tube (T);

characterized by comprising at least one locking valve (7) arranged on said connection line (4).

2. Device according to claim 1, in which said at least one locking valve (7) is piloted by a pressure coming from said pilot line (3).

3. Device according to claim 2, wherein said at least one locking valve (7) is configured so as to adopt a closed position for a pressure lower than a first value and an open position for a pressure above said first value.

4. Device according to any preceding claim, comprising first choking means (C1) arranged in said pilot line (3) between said third port (P3) and said connection line (4).

5. Device according to any preceding claim, wherein said at least one locking valve (7) comprises a two position valve with at least one closed position piloted by elastic means and at least one open position piloted by a pressure coming from said pilot line (3).

6. Device according to any preceding claim, wherein said at least one locking valve (7) comprises a three-position valve with at least one first closed position for a pressure lower than a first value, at least one open position for a pressure comprised between said first value and a second value that is greater than said first value, and at least one second closed position for a pressure that is greater than said second value.

7. Device according to claim 6, wherein said at least one open position is a central position, said at least one first closed position being an outer position piloted by elastic means, said at least one second closed position being an outer position piloted by a pressure coming from said pilot line (3).

8. Device according to any preceding claim, wherein said at least one locking valve (7) comprises a valve with at least two positions that is integrated into a movable element of said control valve (V).

9. Device according to any preceding claim, wherein said at least one circuit element (5) comprises a pressure control valve, for example a maximum pressure valve, and/or a flow control valve, for example a check valve.

10. Device according to any preceding claim, wherein said at least one circuit element (5) comprises a logic element.

11. Device according to claim 10, wherein said logic element is piloted in closure by a pressure in said portion of said hydraulic line (2) and/or by elastic means, and/or in which said logic element is drained by means of an auxiliary drainage line (8) connectable to a drain (R).

12. Device according to any preceding claim, comprising an auxiliary drainage line (8) arranged to drain said circuit element (5) and a fourth port (P4) connected to said auxiliary drainage line (8) and intended for connection to a drain (R).

13. Device according to any preceding claim, comprising second choking means (C2) arranged in said connection line (4) between said circuit element (5) and said pilot line (3).

14. Control circuit of a hydraulic actuator (C), said control circuit comprising a directional control valve (D) of an operating fluid of the actuator, a tube (T) at risk of rupture arranged for connecting said directional control valve (D) to said hydraulic actuator (C), a tube rupture protection device arranged between said tube (T) and said hydraulic actuator (C), and a control device (J) that is manoeuvrable by an operator and simultaneously controls said directional control valve (D) and said control valve (V); said tube rupture protection device (1) being made according to any preceding claim.

15. Use of a hydraulic circuit for the safe descent control, in the case of a tube rupture, of an arm of a working machine, in particular of an excavating and/or load-handling machine, said hydraulic control circuit being made according to claim 14.

Drawing