EP3744984B1

EP3744984B1 - Oleodynamic valve

Info

Publication number: EP3744984B1
Application number: EP20177257.1A
Authority: EP
Inventors: Davide MESTURINI; Ulderico Busani; Alessandro CERVI
Original assignee: Walvoil SpA
Current assignee: Walvoil SpA
Priority date: 2019-05-31
Filing date: 2020-05-28
Publication date: 2023-10-18
Anticipated expiration: 2040-05-28
Also published as: EP3744984A1; IT201900007737A1

Description

FIELD OF APPLICATION OF THE INVENTION

The present invention finds application in hydraulic valves and the object thereof is the realization of a hydraulic circuit suitable, for example, for lifting applications in the presence of valve distributors with multiple functions intended for working machines such as front loaders, shovels, buckets.

BACKGROUND

A common problem in applications with two (or more) uses on working machines such as front loaders, shovels, buckets, etc. .. is the management of the flow rate addressed simultaneously to two sections (boom and bucket). In the traditional parallel configuration, the distribution of the same among the elements depends on the pressures generated by the loads on the uses and therefore potentially, in certain situations, the simultaneousness of the movements is not guaranteed. This problem is more evident when one section controls a lower load downward movement and at the same time the other activated section controls a higher load upward movement. Since it can be complex even for an expert operator to distribute the flow rates directed to the activations with the adjustment spools and guarantee the contemporaneity of said movements, regulation devices equipped with local compensators for each section are known in the state of the art. However, said solution entails an increase in the complexity of the system and an additional cost for the realization of the same. Furthermore, a system with such a precise flow rate partition is not always required for said applications, in particular when the movements take place in the same direction and in opposition thereto.
An example of a hydraulic distributor is described in the European patent application EP 0 393 195 .

EXPOSURE AND ADVANTAGES OF THE INVENTION

The technical problem underlying the present invention is that of providing a hydraulic circuit for a front loader which allows to improve the known solutions and can at least partially overcome one or more of the identifiable disadvantages in relation to the prior art.
A further object of the present invention is to provide a constructively simple solution for a hydraulic circuit equipped with flow rate management capacity addressed simultaneously to two uses in applications on working machines.
It is also an object of the present invention to provide a hydraulic circuit for the front loader capable of working with different modes according to the specific combinations of movements imposed by the operator.
These and other objects are achieved thanks to the characteristics of the invention by means of a hydraulic circuit for front loader according to independent claim 1. The dependent claims outline preferred and/or particularly advantageous aspects of the invention.
It will be appreciated that the circuit according to the present invention provides for the presence of a control device capable of being activated only in the case of specific combinations of movements, restricting the passage area towards the use (or the discharge thereof) at a lower load, while under other conditions of use where the distribution of the flow rates is less problematic or where the spools are activated individually, it does not intervene or its operation is irrelevant. The same control spools are those that enable /disable the device, preferably by closing the passage of the pilot signal, when these are activated in the upward direction.
Thanks to this solution, the control device guarantees an overall operation with a priority activation in which no changes are introduced on each section of the valve system as part of a simple rational solution with a rather low cost.
According to another aspect of the invention, the control device is capable of reducing the passage area towards a use or the discharge of the same in order to distribute the input flow rate equally on two uses activated simultaneously.
The device can be used with various types of circuit supply, in particular both with open centre circuits supplied by fixed displacement pumps and with LS circuits.
On the basis of further preferred aspects, the invention further provides for the application of a same device in two different areas of the circuit itself or different supply apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other features will be more apparent from the following description of some of the embodiments, illustrated purely by way of example in the accompanying drawings, wherein:

Figure 1 represents an example of a 2-section hydraulic circuit for front loader in a "parallel" configuration made according to the prior art;
Figure 2 schematically represents a control device to be inserted in a hydraulic circuit for front loader according to the present invention;
Figure 3 represents the diagram of a hydraulic circuit for front loader with a fixed displacement supply group and a 2-section free-circulation valve distributor with the integration of the control device schematically shown in Figure 2 along a supply line.
Figure 4 represents the diagram of a hydraulic circuit for front loader with a fixed displacement supply group and a 2-section free-circulation valve distributor with the integration of the control device schematically shown in Figure 2 along a discharge line.
Figure 5 represents the scheme of a hydraulic circuit for front loader with variable displacement supply group and LS 2-section valve distributor with the integration of the logic element schematically shown in figure 3 along a supply line.
Figure 6 schematically represents a control device to be inserted in a hydraulic circuit for front loader according to the present invention according to an alternative embodiment.

DESCRIPTION OF THE INVENTION

With reference to the attached figures, a schematic diagram of a control device 1 used in a hydraulic circuit 100 for a working machine, for example a front loader, according to the present invention is illustrated in Figure 2.
The control device 1 comprises a logic element 10 composed of a 2-way 2-position logic element, for example composed of a 2-way 2-position spool, maintained by a spring 2 under a resting condition, i.e. of free passage. A pilot line Pil is also defined in the control device which line receives a decoupled pressure Pd, generated by a pressure reducing member 3 or by an outer supply line.
In a first embodiment, the pressure reducing element 3 is composed of a choke, which is located at a diversion line Ld as a diversion to the supply line LP or said outer supply line. In combination, the pressure reducing element can comprise a pressure reducing valve 31 present inside the control device 1 itself or any device for limiting the flow and pressure on the line Pil.
According to some aspects of the invention, the choke 3 is capable of reducing the passage area along the diversion line Ld, introducing a corresponding pressure loss, with a consequent pressure reduction.
As can be appreciated from Figure 3, which describes a first example of embodiment of the present invention, the hydraulic circuit 100 comprises a plurality of spools C1, C2 ..., Cn connected to respective first uses A1, A2 ... An and second uses B1, B2 ... Bn which together form a control valve distributor 20.
In the example of application on front loaders, the first uses A1, A2 are associated with the upward movement of the arm and bucket of the loader, while the second uses B1, B2 are associated with the downward movement of the same. It is however evident that the same concepts can also be applied to other activations of a working machine, configuring the first and second uses in such a way as to make the relative hydraulic actuator carry out an upward or downward movement, respectively.
In the example of embodiment of the circuit 100 of figure 3, the control device 1 is connected to the spools in such a way that the pilot line Pil passes through all the spools C1, C2 ..., Cn of the control valve distributor 20 through respective hydraulic passages L1, L2, ... Ln up to the discharge T.
It will be appreciated that the control device 1 and the valve distributor 20 can be made by means of a single component, inside which the lines and passages necessary for the realisation of the present invention are made, or, alternatively, the control device can be made as a stand-alone component, combinable with existing valve distributors.
A driving conduit 5 which carries the pilot signal provided by the line Pil to work in opposition to the spring 2 on the device 1 is present downstream said spools C1, C2 ..., Cn along the line Pil. When the spools are not moved or are moved to carry out the downward movement, the hydraulic passage L1, L2, ... Ln is in a state of free passage. Under this condition, the pressure along the driving conduit 5 (except for pressure losses) is similar to that of discharge T and therefore the device remains under a resting condition of free passage.
The spools C1, C2 ..., Cn are configured in such a way that when at least one spool is moved to carry out the upward movement, the relative passage L1, L2, ... Ln is closed. Consequently, the line Pil is no longer connected to the discharge and reaches the pressure of the supply line LP or, if the choke 3 is replaced with or combined with a reducing valve 31, it reaches the set pressure of the reducing valve itself, as well as the pressure along the conduit 5. Since the pressure applied to the active area 5a of the device 1 is now greater than he equivalent pressure value exerted by the spring 2, the logic element switches to the active choked passage position.
The hydraulic circuit for front loader 100 of the example of Figure 3 is of the free circulation type and comprises a fixed displacement pump 6 in parallel configuration. In this case the supply line LP supplies the uses A1, A2 ... An when the spools are switched to carry out the upward movement.
A second supply line LP' is located as a diversion to the supply line LP, which passes through the device 1 and subsequently supplies the uses B1, B2 ... Bn when the spools are switched to carry out the downward movement.
Considering for simplicity purposes two simultaneous movements such as those of a front loader application, the different situations that can occur by activating the two spools simultaneously are illustrated below.
By activating both spools both towards the uses A1 and A2 to carry out the upward movement, the supply flow rate passes entirely through the line LP to the uses themselves, in case the loads imposed by them are different, that is, the consequent flow rate converging to them is different, it is the operator's task to partialize the opening of the spools to compensate for the speed of the same actuations.
By activating a spool towards the use A1 or A2 to move upwards and the other one towards the use B1 or B2 to move downwards, the hydraulic passage L of the spool activated to carry out the upward movement is closed along the line Pil, consequently the device 1 is switched to the active choked passage position. A pressure loss is imposed along the line LP' due to the choked passage itself which helps the operator in partializing the flow rates directed to the two uses, since the pressure difference between upstream and downstream of the slider are now not equivalent, but at least comparable. On the contrary, in a traditional circuit most of the flow rate would be directed to use B which is generally at a lower pressure and it would be very complex for the operator to control both uses in a fluid manner.
By activating both spools towards the uses B1 and B2 to carry out the downward movement, the supply flow rate passes entirely through the line LP' to the uses themselves, without the logic element 10 being activated. In the event that the load imposed by the same is different, that is, the consequent flow rate converging to the uses themselves is different, it is the operator's task to partialize the opening of the spools to compensate for the speed of the actuations themselves.
In the case of a single activation, on the other hand, when the spool is activated to carry out both an upward and downward movement, the operation is similar to the circuit of figure 1.
Figure 4 describes an alternative embodiment of the present invention, in which the control device 1 is inserted inside a hydraulic circuit with a fixed displacement pump in a parallel configuration.
In this case the control device is inserted along the discharge line T' in which drains coming from the first uses A1, A2 ... An converge when the spools are switched to carry out the downward movement. The line T is present downstream the line T' where all the drains coming from the first uses B1, B2 ... Bn converge when the spools are switched to carry out the upward movement connected in turn with the discharge.
The operation of the circuit of Figure 4 during the activation of the spools is illustrated below, being considered for simplicity purposes also in this case two simultaneous movements.
By activating both spools towards the uses A1 and A2 to carry out the upward movement, the operation is the same as for a traditional parallel circuit.
By activating a spool towards the use A1 or A2 to move upwards and the other one towards the use B1 or B2 to move downwards, the hydraulic passage L of the spool activated to carry out the upward movement is closed along the line Pil, consequently the device 1 is switched to the active choked passage position. A load loss is imposed along the line LP' due to the choked passage itself which helps the operator in partializing the flow rates directed to the two uses, since the back pressure at the discharge makes the pressures present on the uses comparable. On the contrary, in a traditional circuit most of the flow rate would be directed to the use B which is at a lower pressure and it would be very complex for the operator to control both uses in a fluid manner.
By activating both spools towards the uses B1 and B2 to carry out the downward movement, the discharged flow rate passes entirely through the line T' which is not choked since the control device is not activated. If the loads on the uses are different, that is, the consequent flow rate converging to the same is different, it is the operator's task to partialize the opening of the spools to compensate for the speed of the actuations themselves.
In the case of a single activation, on the other hand, when the spool is activated to carry out both an upward and downward movement, the operation is similar to the circuit of figure 1.
Figure 5 illustrates a further embodiment variant in which the control device 1 is inserted inside a circuit LS with variable displacement pump 7. The operation of the circuit is similar to that described in the figure.
The solution LS also applies to the case of a logic element 10 located on the discharge line, shown in figure 4.
Figure 6 describes a variant of the control device according to the present invention.
In this case the control device, now generally indicated by the reference number 1', operates in a normally closed rather than open manner, as in the previous embodiments.
In this case, therefore, the spring 2 of the logic element 10 is adapted to keep the logic element 10 in the choked passage position when it is under a resting condition.
In the hydraulic circuit 100, the diversion pressure Pd will therefore preferably be applied to an active area 5a of the logic element 10 that is stressed in the same direction as the spring 2.
The supply pressure P is also copied at a second active area 5b of the logic element 10 in such a way that the force exerted by the spring 2 and the diversion pressure is counteracted by the supply pressure P.
Also in said embodiment, the operation is similar to that previously described.
Following the closure of one of the passages L1, L2, ... Ln the line Pil is closed, reaching the pressure of the supply line LP and making the logic element switch to the second operating position.
The invention therefore solves the proposed problem, at the same time achieving a plurality of advantages, allowing in particular to optimize the management of the flow rate in applications with two or more uses on working machines such as front loaders, shovels, buckets.

Claims

A hydraulic circuit (100) for a working machine, for example a front loader, the working machine including a plurality of hydraulic actuators, said hydraulic circuit (100) comprising:
∘ A supply line (LP) configured so as to receive a supply pressure (P) from a pump (6) associated or associable to a drive distributor;

∘ A plurality of spools (C1, C2..., Cn), each spool being configured to supply said supply pressure (P) in a controlled manner to a corresponding first use (A1, A2...An) and a corresponding second use (B1,B2...Bn) so as to be able to make an actuator of said plurality of hydraulic actuators of the working machine carry out an upward or downward movement, respectively;

∘ a pilot line (Pil) that passes through all the spools (C1, C2...,Cn) through respective hydraulic passages (L1,L2,...Ln) up to a discharge line (T);

the hydraulic circuit further comprising a control device (1) including a logic element (10), which can be switched between a free passage position and a choked passage position,

wherein the control device (1) further comprises a driving conduit (5) configured to switch the logic element (10) between the free passage position and the choked passage position, said driving conduit (5) being connected to said pilot line (Pil), wherein said spools (C1, C2...,Cn) are configured so that when at least one spool of said plurality of spools (C1, C2...,Cn) is in such a position as to make the hydraulic actuator of the working machine carry out the upward movement, a relative passage (L1,L2,...Ln) of the pilot line passing through the spool (C1, C2...,Cn) is closed, so that said logic element (10) is switched from the free passage position to the choked passage position, in that a diversion pressure (Pd) acts on said pilot line (Pil), said diversion pressure (Pd) being:
- either generated by means of a pressure reducing member (3, 31) which is located at a diversion line (Ld), said diversion line (Ld) being provided as a diversion to the supply line (LP),

- or generated by an outer pressure source, the generated diversion pressure (Pd) being led to said pilot line (Pil) by an outer supply line acting as a diversion line, characterized in that said logic element is a 2-position, 2-way logic element.
The hydraulic circuit (100) according to claim 1, wherein said logic element (10) comprises a spring (2) adapted to keep said logic element (10) in said free passage position under a resting condition.
The hydraulic circuit (100) according to claim 2, wherein said diversion pressure (Pd) is applied on an active area (5a) of the logic element (10) that is stressed in an opposite direction with respect to the spring (2).
The hydraulic circuit (100) according to claim 1, wherein said logic element (10) comprises a spring (2) adapted to keep said logic element (10) in said choked passage position under a resting condition.
The hydraulic circuit (100) according to claim 4, wherein said diversion pressure (Pd) is applied on an active area (5a) of the logic element (10) that is stressed in the same direction as the spring (2), and wherein said supply pressure (P) is copied at a second active area (5b) of the logic element (10).
The hydraulic circuit (100) according to any of the preceding claims, wherein said pressure reducing member comprises a choking device (3) adapted to reduce the passage area along the diversion line.
The hydraulic circuit (100) according to any of the preceding claims, wherein said pressure reducing member comprises a pressure reducing valve (31).
The hydraulic circuit (100) according to any of the preceding claims, wherein the spools (C1, C2...,Cn) are configured so that when the spools (C1, C2...,Cn) are in an intermediate position or are switched to such a position as, when the hydraulic circuit (100) is used by a front loader, a downward movement is imparted to the front loader, the pilot line (Pil) is connected to the discharge line (T) so that the pressure along the driving conduit (5) is equal to that of the discharge line (T), unless load losses.
The hydraulic circuit (100) according to any of the preceding claims, wherein said supply line (LP) is configured so as to feed the first uses (A1, A2...An) when the spools (C1, C2...,Cn) are switched to carry out an upward movement of the front loader and further comprising an auxiliary supply line (LP') located as a diversion to the supply line (LP), wherein said auxiliary supply line (LP') passes through the control device (1) and subsequently supplies the second uses (B1, B2...Bn) when the spools are switched to carry out a downward movement of the front loader.
The hydraulic circuit (100) according to any of the claims 1 to 3, wherein the control device is inserted along an auxiliary discharge length (T') into which all the drains coming from the first uses (A1,A2...An) converge when the spools are switched to carry out the downward movement, the discharge line (T) into which the drains coming from the second uses (B1,B2...Bn) converge being present downstream of the auxiliary discharge length (T').