HYDRAULIC APPARATUS

TECHNICAL FIELD.

The invention relates to a hydraulic apparatus, suitable for distributing pressurised fluid in a hydraulic circuit of a work vehicle also under emergency conditions.

BACKGROUND ART.

In work vehicles, used for working both on the fields and worksites, the laws that refer to safety require that such vehicles can be controlled even if the hydraulic units are damaged that take pressurised oil to the various driving and working apparatus on the vehicle. To be able to keep the vehicle under control at all times, the pressurised oil, supplied by a pumping unit, is distributed by suitable hydraulic distributors that see to sending the correct quantities according to the specific operating requirements of the apparatus they are for and complying with certain sending priorities so as to be able to keep the vehicle's steering parts supplied at all times, even to the detriment of the other apparatus, so that control of the vehicles is guaranteed even under emergency conditions such as, e.g., a, leak in the hydraulic c ircui t .

It is also necessary to underline the fact that the work vehicles have different weight and performance, i.e. in other words, they are classified in classes that are normally divided by vehicles of a lightweight class, vehicles of a medium weight class and vehicles of a heavy weight class .

The general standards that govern the construction of work vehicles require, as said above, that when a leak occurs in the hydraulic circuit that supplies the servo driving controls with pressurised oil as well as all the other working apparatus the vehicles are equipped with, it is still possible for the driver to steer for a certain length of time right after the leak occurs so the driver can drive the vehicle over to an area where it cannot generate a hazard due to the leak that has interrupted the supply of pressurized oil to the servo controls that operate the steering units, making the vehicle uncontrollable after a very short period of time. ^■ in the case of vehicles belonging to the light weight class, the problem is felt less because, due to the relatively light weight of such vehicles, they can still be driven even under emergency conditions and without the action of servo mechanisms that are designed for this purpose and mounted on the vehicles even though the effort required of the driver is quite considerable . In vehicles belonging to the medium weight class, hydraulic driving units are mounted that operate the steering parts of the vehicle and that are supplied with a dual displacement of oil from the pumping units: a higher displacement is supplied under normal operating conditions so steering is possible with only small turns of the steering wheel, a smaller displacement is supplied under emergency conditions to ensure the steering parts are supplied even if the steering wheel has to be turned a lot just for tiny steering manoeuvres.

In vehicles belonging to the heavy weight class, two pumping units are tniDunted in such a way that they are independent, one main unit and one auxiliary unit. The main pumping unit is operated by the vehicle's engine and supplies the servo controls of the steering units and the working apparatus during normal operation of the vehicle, while the auxiliary pumping unit, which is connected to the transmission parts that transmit movement to the wheels from which it receives motion in order to be able to work, supplies small quantities of pressurised oil under emergency conditions so that, when there is a leak, the vehicle continues moving by inertia transmitting movement to the auxiliary pumping unit which, in turn, is able to supply a sufficient quantity of oil to allow a few steering manoeuvres before the vehicle stops once and for all . This state of the art has some drawbacks.

A first drawback concerns the medium vehicle class: the dual displacement steering units are very expensive and influence the overall cost of the vehicles . Besides this, under emergency conditions, these dual displacement steering units, while they dp allow steering also under critical conditions they require, in order to do so, a lot of turning of the steering wheel with considerable physical effort by the driver.

In addition, these dual displacement pumping units are able to solve the problem of supplying with oil to the steering servo controls of vehicles in the medium class only, since their structure is

such that it cannot operate the driving servo controls of vehicles in the heavy class under emergency conditions.

A second drawback appertaining to vehicles belonging to the heavy class is that the auxiliary pumping units are also very expensive and are an additional element that has to be mounted on the vehicles . In addition, these secondary pumping units, as they are continuously operated by the movement of the . wheels also when they are not required, continuously absorb a considerable amount of engine power which, however, in the greatest part of the vehicles' use cycle, is not used- In addition to the above, if the pumping parts are set to supply several working apparatus mounted on the vehicle and they require different oil pressures, it could happen that the servo controls that operate the steering parts are sent oil at a pressure that is too high which could damage them: thus, it is necessary to lmount an additional pressure compensating device that limits the pressure of the oil sent to the servo controls that operate the steering parts, e.g. by reducing the flow of oil.

OBJECTS OF THE INVENTION.

One object of the invention is to improve the state of the art. _:

Another object of the invention is to provide a hydraulic apparatus that allows pressurised oil to be supplied to the servo controls that operate the vehicle's steering units under emergency conditions without, however, it being necessary to

mount dual dj s,g|. _$ .fβjnea pimping units / or the auxiliary type, coupled units. According to one aspect of the invention a hydraulic apparatus is provided comprising: pumping means for pumping a fluid at a first pressure; user means of said fluid at said first pressure; emergency supply means connectable to said user means activating a connection; activation means of said connection that can be operated at a second pressure of said fluid different from said first pressure and interposed between said user means and said emergency supply means, characterised by the fact that said activation means have a first connection configuration wherein both said pumping means and said emergency supply means are connected to said user means .

The hydraulic apparatus therefore allows, under emergency conditions, the user means to be supplied, such as the servo controls that activate the vehicle's steering units, in particular of work vehicles, with quantities of pressurised oil such to guarantee the possibility of continuing to drive the vehicles also under emergency conditions like, e.g. , in the case of a leak in the hydraulic circuit which activates hydrostatic power steering and for a length of time that is enough to drive them in complete safety; at the same time, the hydraulic apparatus avoids that excessively pressurised oil reach the servo controls or that oil leaks occur,- in fact, the oil, under emergency conditions, must be totally available. for supplying the servo controls that operate the vehicle's steering units.

BRIEF DESCRIPTION OF THE DRAWINGS.

Further characteristics and advantages of this invention will appear more evident from the detailed description ©f a hydraulic apparatus, illustrated for information purposes only and non limiting, in the enclosed drawing tables enclosed, wherein :

Figure 1 is a block diagram of a hydraulic circuit that has one hydraulic distributor and a tank to hold pressurised oil usable in an emergency condition to supply a hydraulic apparatus like, e.g., the hydrostatic power steering of a vehicle; Figure 2 is a diagram of a hydraulic circuit that comprises the hydraulic apparatus of Figure 1 and in an emergency condition and where a supply line of pressurised oil to a user apparatus is controlled by the hydraulic distributor in a four port connection version; Figure 3 is a diagram of a hydraulic circuit with the hydraulic apparatus of Figure 1 in an emergency condition and where a supply line of pressurised oil to a user apparatus is controlled by the hydraulic distributor in a five port connection version; Figure 4 is a diagram of a hydraulic circuit with the hydraulic apparatus of Figure 1 in an emergency condition and where a supply line of pressurised oil to a user apparatus is controlled by the hydraulic distributor in a six port connection version;

Figure 5 is a diagram of a hydraulic circuit with the hydraulic apparatus of Figure 1 in an emergency condition and where a supply line of pressurised oil to a user apparatus is controlled

by the hydraulic distributor in a s e ve n p o r t connection version; Figure 6 is the hyc raulic diagram of Figure 2 to which a fifth port has been added for connecting to another user apparatus;

Figure 7 is the hyc raulic diagram of Figure 4 to which a seventh port has been added for connecting to another user apparatus;

Figure 8 is the hyc raulic diagram of Figure 4 in which a second version of the emergency supply means has been inεerted,-

Figure 9 is a hydrE.ulic diagram of the hydraulic apparatus of Figure 3, comprising another part for supplying other u ser apparatus according to defined priorities and a part for recharging emergency supply means

Figure 10 is a Iongitudinal section view of the activation means c f connections among pumping means, user means ax d emergency supply means, in a five port version and in an emergency condition

Figures 11, 12 and 3 3 are longitudinal sections of activation means of the connections among pumping means, user means and emergency supply means in six port version in an emergency configuration, a normal operating con figuration and in a protection configuration respectively ;

Figure 14 is a longitudinal section view of the activation means of connections among pumping means, user means and emergency supply means, in a seven port version and in an emergency condition.

EMBODIMENTS OF THE INVENTION.

With reference to Figure 1, ST indicates a known hydraulic user apparatus, hereinafter referred to briefly as user

apparatus ST like, e.g., the hydrostatic power steering 3 of a work vehicle, more specifically an agricultural tractor. The user apparatus ST is supplied by a pump 2, designed to pump oil at a first pressure ^W P" towards the hydrostatic power steering 3.

The pump 2 is connected to the hydrostatic power steering 3 by means of a hydraulic circuit indicated in its totality with 4 in the Figures and between the hydrostatic power steering 3 and the pump 2 a line is contemplated for measuring pressures, known by the name of "load sensing line", in this case "load or pressure value" indicated with 5 and is able to transmit to the pump 2 pressure value variations which occur inside the hydrostatic power steering 2 when it is operated by the driver when he/she has to turn the steering wheel.

With reference to Figures 2 to 5, a hydraulic apparatus l is illustrated delimited by the dotted lines 1'.

According to the invention, it can be noted that between the hydrostatic power steering 3 and the pump 2 a hydraulic distributor 6 is interposed that comprises a sliding body, indicated in the diagrams of Figures 1 - 5 and in the sections of Figures 6 - 8 with the numerical reference 7, inside which a sliding seat 107 has been obtained; in this seat 107 a cursor 8 is arranged, that is mounted in a sliding way and ready to open and close, according to pre-established sequences, a set of ports obtained in the sliding body 107, designated to connect together, according to pre-established requirements, by means of the sliding of the cursor 8, the hydrostatic power steering 3, the pump 2, the "load sensing line" 5 and an emergency supply unit, indicated as a whole with 109.

According to a first version of the hydraulic apparatus 1, this emergency supply unit 109 comprises an accumulator 9

inside which pressurised oil is accumulated and which ia rechargeable by the pump 2 as will be explained further on.

According to an alternative embodiment of the hydraulic apparatus 1, the accumul ifcor 9 can be substituted by another pump, not illustrated in the drawings as it is known by the technicians in the sector, set to supply pressurised oil when the cursor 8 moves into the position contemplated for this and described further on. The hydraulic distributor 6 has three distribution positions which are represented in the diagrams by three box sectors positioned one after the other: a first position is indicated by the sector 106, a second is indicated by the sector 206 and a third is indicated by the sector 306. The sliding body 7 of the distributor 6 can have, in accordance with different versions of possible embodiments, a predefined number of access ports to the sliding seat 107 : this predefined number can vary from four ports, as in the version illustrated in Figure 2, to five ports, as in the version illustrated in Figure 3, to six ports, as in Figure 4, to seven ports, as in the version illustrated in Figure 5. The functions of the various ports will be described . in detail further on. with reference to Figures 6, 7, S, a first port is indicated with 50 that connects the pump 2 to the sliding seat 107; 60 indicates a second port that connects a first stretch 105 of the "load sensing" line 5 coming from the hydrostatic power steering 3 to the sliding seat 107; 70 indicates a third port that connects the accumulator 9 to the sliding seat 107; 80 indicates a fourth port that puts the hydrostatic power steering 3 in communication with the sliding seat 107 for the supply; 90 indicates a fifth port that puts in communication a second stretch 205 of the "load sensing" line 5 that takes a pressure signal or a modification signal of the pressure values from the sliding seat 107 to the pump 2.

The sliding seat 107 has one end facing left for those looking at the Figures 6 to 8 , which is closed with a cap 30 thus defining a chamber 400 between the cap 30 and a first end 108 of the cursor 8, while, the second opposite end, facing right for those looking at Figures 6 to 8, is closed with a tang 31 screwed into it and inside which a second hollow seat 32 is formed axially which houses a first spring 15, that can be loaded by compression. The latter has one end that rests on a closed bottom 33 of the tang 31, while the opposite end rests on a spring-guide body 34 which is made so it can rest alternatively against the second end 208 of the cursor 8 or against a shoulder or stroke stop 18, obtained in the sliding seat 107. The spring-guide body 34 has inside a third hollow seat 35 in which a second spring 16 is housed, which is contained at one end by a closed bottom 36 of the third hollow seat 35 while the other opposite end by a slot 308 made in the second end 208 of the cursor 8. This cursor 8 is crossed by an axial pipe 37 from which, in a transversal and substantially perpendicular direction, proceeding in the direction from the cap 30 towards the tang 31, first radial openings 38, second radial openings 39 and a third radial opening 40. In addition, peripherally the cursor 8 has a first annular groove 41 and a second annular groove 42 and, at the end facing the cap 30, a passage 401 that connects the pipe 37 to the chamber 400 by the interposition of a constriction 402. The height of the first annular groove 41 is such that, when required, it is possible to connect together the first port 50, through which pressurized oil is sent from the pump 2, and the fourth port 80 connected to the hydrostatic power steering 3 , as can be seen in Figure 6 and in Figure 7. The height of the second annular groove 42 is such that, when required, it is possible to connect together the second port

60 and the fifth port 90 from where the second stretch 205 of the "load sensing" line 5 comes out.

Thus, in tfte position o:E the cursor 8 illustrated in Figure

7, the latter is kept balanced between the thrust of the oil pressure in the chamber 400, which acts on the thrust surface of the first end 108 of the cursor 8, and the counter-thrust of the springs 15 and 16 which act together with that of the oil of the ^w load sensing" line coming from, via the first stretch 105 of the latter, the hydrostatic power steering 3 through the second port 60 and going towards the fifth port 90.

In this position of the cursor 8, or normal operating position, it can be een that the pump 2 supplies the hydrostatic power steering 3 by thrusting pressurised oil, precisely at a first pressure *P" , through the first port 50, the first annular groove 41, from where the oil goes through the first radial openings 38 and from these, through the axial pipe 37, to the f|ourth port 80 and, from here, to the hydrostatic power steering 3. It can also be seen that in this position of the cursor 8, the third port 70 is completely closed by the cursor 8 while the second port 60, whidh is constantly in communication with the second hollow seat 32 by means of a derived pipe 43, normally controlled by a constriction 44, is partially connected both to the fifth port 90, by means of the second annular groove 42, and to the hydrostatic power steering 3 by means of the third radial opening 40 and the axial pipe 37. In the emergency position of the cursor 8, schematically indicated in Figure 4 and in the corresponding longitudinal section of Figure 6, it can be seen that the cursor 8 has the sector 106 aligned with the pump 2 which is still connected to the hydrostatic power steering 3 by means of the hydraulic circuit 4.

Together with this, it can be seen that the accumulator 9 is also connected to the hydrostatic power steering 3 by means of the second radial openings 39, the axial pipe 37 and the first radial openings 38; in this way, even if the hydraulic 5 circuit 4 is damaged and leaks oil, a sufficient volume of pressurised oil coming from the accumulator 9 can still reach and operate the hydrostatic power steering 3 , albeit for a limited number of operations. The pressure of the oil in the hydraulic circuit 4 becomes,

1.0 in this emergency condition, very low due to the leak and, therefore, the pressure "P" inside the chamber 400 and which acts through the branch 104 on the corresponding transversal thrust surface of the first end 108 of the cursor 8, is very limited; for this reason, the pressure "Pl" which acts on the

15 transversal thrust surface of the opposite end 208 and, above all, the thrust of the second spring 16, are sufficient to keep the cursor 8 in this emergency position 106, while the first spring 15 remains inactive, being blocked by the shoulder or stroke stop 18 designed for this purpose in the

20 sliding body 7.

With reference to Figure 6 where the emergency condition is illustrated schematically in Figure 4 , it can be seen that the position of the cursor 8 is such to keep the connection open between the pump 2 and hydrostatic power steering 3, by

25 means of the hydraulic circuit 4, the first port SO, the first annular groove 41, the axial pipe 37, the first radial openings 38 and the fourth port 80.

However, the fast drop in pressure inside the chamber 400, which is transmitted to it through the first port 50, the

30 first radial openings 38 and the axial pipe 37, and the consequent progressive movement of the cursor 8 until it comes to rest against the cap 30, opens the connection also between the second radial openings 39 and the third port 70,

putting in communication the accumulator 9 with the hydrostatic power steering 3 through the axial pipe 37. In this emergency condition, therefore, some of the oil sent by the pump 2 but, above all the oil contained in the accumulator 9, reaches the hydrostatic power steering 3 which allows the driver to operate the hydrostatic power steering 3, albeit for only a few operations, but which is enough to drive the agricultural tractor over to a safe area like, e.g., a parking area . In this emergency configuration, the first spring 15 is inactive with respect to the second end 208 because the cursor S is completely over against the cap 30 and the spring-guide body 34, as can be seen in Figure 4 and also in Figure 6, is resting against the shoulder or stroke stop 18 obtained in the sliding seat 107.

The protection position illustrated in Figure 8 again in the longitudinal section, is reached when, starting from the normal operating position illustrated in Figure 7, the pump 2 starts supplying oil at a pressure "P2" that is greater than the normal operating pressure "P" and that the hydrostatic power steering 3 is able to withstand: this condition occurs when, e.g., a working device on the agricultural tractor has to be operated and which must be supplied with oil at operating pressure ^W P2" and that the pump 2 starts supplying as soon as this working device is operated.

With reference to Figure 8 which illustrates this protection condition, it can be seen that the cursor 8 is already in the protection position indicated by the sector 306 in Figures 2

5; in this position, both the first port 50, and consequently the hydraulic circuit 4, and the third port 70, and consequently another hydraulic circuit 17 that connects the accumulator 9 to the sliding seat 107, are interrupted by the cursor 8 and, therefore, oil at pressure "P2" cannot reach the hydrostatic power steering 3 while the oil that is

in the hydraulic circuit 4 is drained slowly towards a discharge 300 through a connecting section 19 that is an extension of the axial pipe 37 to reach the third radial opening 40.

The movement of the curfeor 8 into the protection position of the hydrostatic power ε teering 3 occurs because the oil at pressure "P2", which is supplied by the pump 2 when a working device of the agricultural tractor is operated and indicated with 11 or 12 in Figure 9, instantly invades the chamber 400 seeing as the cursor 8 is in the normal operating condition illustrated in Figure 7.

The thrust that this pressure "P2" generates almost instantly on the transversal thrust surface of the end 108 of the cursor 8 is greater than the opposing thrust generated globally by the action of the pressure "Pl", which reaches inside the second hollow seat 32 coming from the first stretch 105 of the "load sensing" line 5, through the second port 60 and the branch 104, and that of the springs 15 and 16 which act on the same second end 208. When the cursor 8 moves into the protection position illustrated in Figure 8, it can be seen that both the first spring 15 and the second spring 16 are compressed in an axial direction, between, respectively, the slot 308 and the closed bottom 36 of the spring-guide 34 and between this and the closed bottom 33 of the tang 31.

With reference to Figure 9 it can be seen that the hydraulic apparatus is completely contained inside the dotted line 100. The hydraulic apparatus, indicated in this case with reference number I', also comprises further priority hydraulic distributor 10 designed to supply pressurised oil - according to a pre-established sequence - not only to the hydrostatic power steering 3 but also to the two additional devices 11 and 12 , comprising, e.g., a braking unit and a lifting device mounted on the agricultural tractor.

in the hydraulic apparatus 1' a recharge valve 13 is also designed to recharge the accumulator 9 in certain conditions. The pump 2, therefore, sends pressurised oil both towards the hydraulic distributor 6 through the hydraulic circuit 4 and towards the further hydraulic distributor 10 through a supply branch 17' , from which a derivation branch 506 starts, reaching a first end 110 of the further hydraulic distributor 10. On an opposite end 210 of the further distributor 10 an additional hydraulic branch 507 acts which is supplied as will be described further on.

This further distributor 10 has numerous distribution positions and has one inlet port 610 and two outlet ports, 710 and 810 respectively, which are connected to the additional device 12, by means of a branch 117'' _/ and to the recharge valve 13 with a branch 117' .

The operation of the further priority hydraulic distributor 10 is known and inconsequential for this invention and so is not described in any further detail . It should however be noted that on the transversal pressure surface of the opposite end 210, an oil pressure value acts that reaches it through the additional hydraulic branch 507: this pressure value is the greatest of the pressure values selected out of the two that reach a valve 310 in which the second stretch 205 of the "load sensing" line 5 and one branch of the circuit 510 derived from the supply branch 117' are channelled, immediately upstream from a uni-directional valve 500 mounted inside the recharge valve 13 as described further on. Basically, the further distributor 10 is moved by differences between pressure values acting on the opposite ends 110 and 210.

The recharge _* va3.ve 13 has three working positions, indicated by sectors 113, £13 anj| m respectively or, briefly, by position 113, 213 and 313.

In position 113 which is the position in which the accumulator 9 is recharged and which, therefore, is a recharging position, the supply branch 117', which comes from the further priority hydraulic distributor 10 coming out of the port 810 and which is controlled by the latter, is connected to the accumulator 9 by means of a connecting branch 17" and, hence, is connected also to an additional accumulator 9' which is associated to the additional device 11.

In this position 113, on the supply branch 17', one unidirectional valve 500 is mounted, as mentioned previously, which has the function of preventing the oil returning to the pump 2; also on one outlet branch from the recharge valve 13 and indicated with 17' ', a uni-directional valve 501 is mounted which, in turn, has the function of preventing the pressurised oil in the accumulator 9 from returning to the recharge valve 13.

The latter comprises, as is known, a valve body inside which a distributor body 505 is mounted in a sliding manner which moves between the three working positions 113, 213 and 313. The movement of this distributor body 505 occurs due to the pressure stresses that act on its opposite ends, with pressure forces generated respectively by a counter spring 502, which has an adjustable force, and by the oil that acts on the opposite end through one circuit branch 17' ^{; /} derived from the outlet branch 17' '. In position 113 illustrated in Figure 9, it can be seen that the pump 2 is connected to the accumulators 9 and 9' : hence, in this position, the latter are recharged.

When recharging is completed, the pressure inside the outlet branch 17'' and the circuit branch 17''' increases causing

the cursor 505 to move up to position 313 where the supply of pressurised oil is interrupted.

When the value of the oil pressure inside the outlet branch 17'', and hence 17''', exceeds a preset loading value of the counter spring 502, the distributor body 505 moves into the position 213.

In this position the pump 2 is still connected to the accumulator 9, while the circuit branch 510 is connected to a discharge 504; because of this, at the valve 310 arrives only the pressure value of the pump 2 which, together with an auxiliary spring 520, presses on the end 210 pushing the priority hydraulic distributor 10 gradually towards a closing configuration of both outlet ports 710 and 810, hence reducing, until it stops, the supply of oil at pressure "P" to the accumulators 9 and 9' : this position 213 defines a condition considered as standby.

If the pressure inside the additional circuit 17' , and consequently inside the outlet branch 17'', continues to increase, e.g., because an increase in the flow rate is required of the pump 2 in order to activate the additional device 12 and the priority hydraulic distributor 10 has moved into a supply configuration of this additional device 12, this pressure also acts on the distributor body 505, via the branch IV'', moving it into position 313 and winning against the resistance of the counter spring 502.

As can be seen, in this position 306 the passage line 117' is closed and the branch 510 is connected to the discharge 504; the outlet branch 17' ' is also connected to the discharge 504, by means of a connection 525 in the distributor body 503 and which connects together, in position 313, the passage line 117' and the outlet branch 17'': this position 313 is, therefore, a position that protects the accumulator 9 against excessive over pressures in input that exceed the pressure value the accumulator 9 can tolerate.

Hence, in this position 306, fhe pump 2, due to the cursor 505 moving into position 313, and the accumulator 9, due to the cursor 8 moving into position 306, cannot send any more oil at pressure "P2" generated by the pump 2 to operate the additional device 12 towards the hydrostatic power steering 3 , which is thus protected against damage .

The oil at pressure *P2" is then drained slowly from the chamber 400 through the pipe 37, the connecting section 19 controlled by a constriction 119, the third radial opening 40 and the second annular groove 42 that opens the connection between the latter and the additional opening 90, from where the second stretch 205 of the ^M load-sensing" line 5 starts that carries the drained oil back to the pump 2, until inside the chamber 400 is restored the pressure value "P" at which the hydrostatic power steering 3 can work.

When this condition is reached, the cursor 8 moves again in the direction of the cap 30, until it is once again in the normal operating condition indicated in Figure 7.