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Patent Searching and Data


Title:
LOAD HOLDING VALVE
Document Type and Number:
WIPO Patent Application WO/2013/150431
Kind Code:
A1
Abstract:
A load-holding valve (1) comprises: a body (2) provided with a cavity (8); a piston (30) that is bidirectionally movable inside the cavity (8); a movable seat (22), hollow and surrounding the piston (30), positioned inside the cavity (8) and arranged for interacting with the piston (30) such as alternatively to permit said pressurized fluid, or prevent the pressurized fluid from, traversing a passage zone (As) interposed between the seat (22) and the piston (30); a plurality of openings (3, 4, 5) obtained in the body (2), through which a pressurized fluid can enter, or exit from, the valve (1). At least one of the openings (3, 4, 5) is suitable for connecting an intermediate portion (33) of the piston (30) with actuating means that is associable with the valve (1), and the intermediate portion (33) is interposed between an end portion (34) of the piston (30) and the seat (22). The valve (1) is characterized in that the end portion (34) has a maximum transverse dimension (Dp) that is greater than an internal maximum transverse dimension (Ds) of the seat (22).

Inventors:
STORCI CHRISTIAN (IT)
Application Number:
PCT/IB2013/052542
Publication Date:
October 10, 2013
Filing Date:
March 29, 2013
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ATLANTIC FLUID TECH S R L (IT)
International Classes:
F16K31/122
Foreign References:
US20110101772A12011-05-05
US20090065727A12009-03-12
Other References:
None
Attorney, Agent or Firm:
CRUGNOLA, Pietro et al. (Viale Corassori 54, Modena, IT)
Download PDF:
Claims:
CLAIMS

1. Load-holding valve (1), comprising:

a body (2) provided with a cavity (8),

a piston (30) that is bidirectionally movable inside said cavity (8), a movable seat (22) positioned inside said cavity (8) and arranged for interacting with said piston (30) such as alternatively to permit said pressurized fluid, or prevent said pressurized fluid from, traversing a passage zone (As) interposed between said seat (22) and said piston (30), said seat (22) being hollow and surrounding said piston (30), a plurality of openings (3, 4, 5) obtained in said body (2), through said openings (3, 4, 5) a pressurized fluid being able to enter in, or exit from, said valve (1) and at least one of said openings (3, 4, 5) being suitable for connecting an intermediate portion (33) of said piston (30) with actuating means that is associable with said valve (1), said intermediate portion (33) being interposed between an end portion (34) of said piston (30) and said seat (22),

characterised in that said end portion (34) has a maximum transverse dimension (Dp) that is greater than an internal maximum transverse dimension (Ds) of said seat (22).

2. Valve (1) according to claim 1, wherein said piston (30) comprises a first part (30a) and a second part (30b), said first part (30a) and said second part (30b) being joined together.

3. Valve (1) according to claim 1, or 2, wherein said plurality of openings (3, 4, 5) comprises a first opening (3), a piloting opening (4) and a second opening (5), said second opening (5) being suitable for connecting said intermediate portion (33) to said actuating means and being interposed between said first opening (3) and said piloting opening (4).

4. Valve (1) according to claim 2, or 3, wherein said second part (30b) comprises said intermediate portion (33) and said end portion (34).

5. Valve (1) according to any preceding claim, wherein said seat (22) comprises an internal wall (22a) defining said internal maximum transverse dimension (Ds).

6. Valve (1) according to any preceding claim, wherein said piston (30) further comprises a head portion (32) and a connecting portion (52), which is arranged near said seat (22), said connecting portion (52) comprising a first zone (52a) and a second zone (52b).

7. Valve (1) according to claim 6, as appended to claim 5, wherein said passage zone (As) is overall defined, in use, by said seat (22) and by said piston (30) when said second zone (52b) is spaced apart from said internal wall (22a).

8. Valve (1) according to claim 6, or 7, wherein said second zone (52b) comprises a portion (46), said portion (46) being positioned inside said seat (22) when, in use, said connecting portion (52) contacts said seat (22).

9. Valve (1) according to any preceding claim, wherein said end portion (34) comprises an annular face (47), said annular face (47) facing said intermediate portion (33).

10. Valve (1) according to claim 9, as appended to claim 8, wherein the area of said annular face (47) is greater than the area of said portion (46).

11. Valve (1) according to any preceding claim, comprising a safety valve (10) arranged for detecting a pressure of said fluid near said intermediate portion (33) and for opening if said pressure overcomes a predetermined threshold value.

Description:
Load holding valve

The invention relates to a load-holding valve traversed by a pressurized fluid.

The load-holding valves are piloted valves that are typically employed in the field of the earthmoving machines. These valves are arranged for holding suspended loads being also very heavy, such as, for example, an excavator articulated arm, as well as for keeping the above-mentioned loads suspended in a desired position for a preset time interval.

These valves are fed and traversed by a pressurized fluid, which is sent to an actuator, generally a double-action hydraulic piston, which in turn is connected to the arm to be supported.

The known valves comprise a main channel, extending longitudinally along a valve body, inside which various known components - among which a piston and a seat are received, both being longitudinally movable - arranged to permit or prevent the passage of said pressurized fluid as a function of their mutual arrangement.

A plurality of openings is obtained in the valve body, each of which is in communication with the main channel through a respective duct, and it is arranged to permit said pressurized fluid entering in or exiting from the valve. Therefore, the known valves comprise a first opening and a second opening through which, in a lifting step of the load, the pressurized fluid respectively enters the valve body and exits from the latter to reach the actuator. On the contrary, in a lowering step of the load, the pressurized fluid enters the valve through the second opening and exits the valve through the first opening. In use, the flow of the pressurized fluid - when the latter has its typical operative pressure - from the second opening towards the first opening would not, however, be permitted due to the mutual arrangement of the above-mentioned known components. When the suspended load has to be lowered, it is then provided to pilot the valve, so as to permit said pressurized fluid reaching the valve from the actuator exiting through the first opening.

In the piloting step, further pressurized fluid is delivered into the valve body through a piloting opening, which further pressurized fluid acts on the piston and pushes it in such a position as to permit the above-mentioned fluid flow from the second opening to the first opening. On the piston, particularly on the piston zone cooperating with the seat in which the passage for the pressurized fluid is defined, a thrust force further acts, which is exerted by the pressurized fluid flow entering the valve through the second opening.

In the piloting step, the piloting force exerted on the piston by the further pressurized fluid is concordant with the above-mentioned thrust force, so that both the above-mentioned forces are able to overcome an elastic force that is opposite them and that is exerted by a spring on the piston.

A drawback of the known valves is that they lack safety devices to block the movement of the suspended load in the case of breakages or structural failures of a valve component, particularly, the spring. In use, the latter is very stressed; therefore, it may occur that one or more spring coils are damaged, for example, at surface cracks that cause the successive spring breakage. When this occurs, the elastic force exerted by the spring on the piston suddenly ceases, and the piloting and thrust forces are not opposed anymore. The piston is consequently kept far away from the seat, and the passage for the pressurized fluid flow from the second opening to the first opening remains open therebetween. Consequently, the suspended load suddenly and quickly lowers, until the hydraulic piston reaches the end stroke position.

The sudden and quick lowering of the suspended load can be dangerous for anything being present in the surrounding environment, which can be hit or impacted by the load. Therefore, it is apparent that this is certainly to be avoided, for both preserving people's safety, and for not damaging, even severely, objects such as, for example, machineries, buildings, etc.

Another drawback of the known valves is that they are not able to control and adjust in a safe and effective manner the lowering step of the suspended load, particularly when the latter is running the final length of its stroke. As the suspended load is inclined, the pressure of the fluid entering the valve from the second opening increases, being able to reach values that are even significantly high. This causes a consequent increase of the thrust force on the piston by the above-mentioned fluid, which causes the lowering speed of the suspended load to considerably increase. This effect is particularly unwanted by the operators, since it makes the lowering operation of the suspended load more complex to be controlled.

An object of the invention is to improve known piloted valves.

Another object is to provide a load-holding valve that allows blocking the movement of the suspended load, if the spring acting on the piston in opposition to the piloting force and the thrust force of the pressurized fluid flow breaks.

A further object is to provide a load-holding valve in which it is possible to compensate for pressure increases of the fluid entering the valve to avoid corresponding speed increases during the lowering of the suspended load.

According to the invention, a load-holding valve as defined in claim 1 is provided. The invention will be able to be better understood and implemented with reference to the appended drawings, which show an exemplary, non-limiting embodiment thereof, in which:

Fig. 1 is a longitudinal section of a valve according to the invention, illustrated in a first operative configuration;

Fig. 2 is a section as the one of Fig. 1, in which the valve is illustrated in a second operative configuration;

Fig. 3 is an enlarged schematic view of a piston and a seat comprised in the valve of Fig. 1, in which the forces acting on the piston are highlighted.

Figs. 1-3 show a piloted valve 1 in a first operative configuration K .(Figs. 1 and 3) and in a second operative configuration J (Fig. 2).

The valve 1 comprises a body 2 provided with a plurality of openings through which the pressurized fluid can enter, or exit from, the valve 1. Therefore, these openings enable the valve 1 to be connected to a hydraulic circuit of a machine (not shown), for example, an earthmoving machine. In particular, a first opening 3, a piloting opening 4, and a second opening 5 are visible, the function of which will be explained in detail herein below.

A cavity 8 is made in the body 2, extending in a substantially parallel manner to a first longitudinal axis A of the valve 1. The cavity 8 comprises a plurality of portions having, for example, a substantially cylindrical transversal section. The portions have diameters different from one another and are made in sequence along the axis A.

The first opening 3 is connected to the cavity 8 by means of a first channel 3 a, the piloting opening 4 is connected to the cavity 8 by means of a piloting channel 4a, and the second opening 5 is connected to the cavity 8 by means of a second channel 5a. The latter is a through channel connecting two opposite walls of the body 2, and it is closed - on an opposite side to the second opening 5 - by a safety valve 10, the function of which will be explained in more detail herein below. The piloting channel 4a comprises a first portion 4b, which is orthogonal to the axis A, and a second portion 4c, communicating with the first portion 4b and leading into the cavity 8. The first portion 4b may comprise a dowel 6 arranged for being traversed by the pressurized fluid. The valve 1 further comprises a connection channel 26 allowing connecting the piloting channel 4a with the second channel 5a when the safety valve 10 (interposed therebetween) is in the open position. In a non-illustrated version, the valve 1 lacks the safety valve 10. In this case, the second channel 5a is not a through channel, or it is closed by a closing member, such as, for example, a threaded plug. Furthermore, this version of the valve lacks the connection channel 26.

The valve 1 comprises a containing element 16, partially received inside the cavity 8 and partially projecting outside the valve body 2. The containing element 16 is fixed to the body 2 through a threaded connection 17. A thread is made on an external side wall portion of the containing element 16, which thread is arranged to couple with a respective thread formed on an internal side wall of the cavity 8. The containing element 16 is internally hollow, so as to define a chamber 61 inside it.

Externally to the containing element 16, a second sealing member 20 is arranged, for example, an "O-ring" in polymeric material, which enables the cavity 8 to be sealingly closed. The containing element 16 is provided with an internal end 21 , on which a plurality of passages is made. The passages are shaped as half-circular recesses, and they are obtained in sequence on an end edge of the end 21, which is shaped as a hollow cylinder. The valve 1 further comprises a piston 30, extending in a substantially parallel manner to the first longitudinal axis A and being received inside the cavity 8. The approximately cylindrical piston 30 is bidirectionally movable according to the directions indicated by the arrows X and Y, parallel to the axis A. The piston 30 comprises a head portion 32, which is enclosed inside the containing element 16, an intermediate portion 33, and an end portion 34. The intermediate portion 33 has a transversal dimension that is less than the head portion 32 and the end portion 34. Between the head portion 32 and the intermediate portion 33, a connecting portion 52 is interposed, arranged near the end 21, and comprising a first zone 52a and a second zone 52b, both having an approximately frusto-conical shape (Fig. 3).

In other embodiments, not illustrated, the first zone 52a and the second zone 52b can be shaped in a different manner, while maintaining a transverse dimension greater than the adjacent head portion 32 and intermediate portion 33.

In the chamber 61 of the containing element 16 a spring 41 is housed, acting on a centering member 42 pressing on the piston 30, particularly on a bottom wall of the head portion 32. The centering member 42 is substantially conical-shaped, i.e., it is shapingly coupled with the above-mentioned bottom wall, and it ensures that the elastic force FEL exerted by the spring 41 on the piston 30 is balanced, i.e., substantially directed along the axis A. The spring 41 is pre-loaded, and it is kept compressed by a thrust member 43, which is fixed to the internal side wall of the containing element 16 by a threaded coupling 67. On the thrust member 43, a plug 44 is screwed, by acting on which an operator can adjust the spring 41 preload.

A movable seat 22 is further received in the cavity 8, which is shaped as a bush, and thus it is internally hollow, arranged near the end 21 of the containing element 16 and the connecting portion 52. The seat 22 comprises an internal wall 22a, defining an internal maximum transverse dimension D s of the seat 22 and facing the piston, and an external wall 22b, contacting the walls of the cavity 8. (Fig. 3)

An annular seat 23 is made in the external wall 22b, in which a second sealing member 24 (Fig. 3) is housed, which enables the passage of the pressurized fluid to be prevented outside the seat 22.

The seat 22 surrounds the piston 30, particularly near the second zone 52b and the part of intermediate portion 33 contiguous thereto. Therefore, according to the position of the piston 30, the latter can completely occlude, or not, a passage zone A s for the pressurized fluid, which is interposed between the seat 22 and the piston 30. More precisely, the passage zone A s is overall defined by the seat 22 and the piston 30 when the second zone 52b does not contact, i.e., it is spaced apart from, the internal wall 22a of the seat 22, thus enabling the passage of the pressurized fluid from the second channel 5a towards the first channel 3a. On the contrary, when the second zone 52b contacts the internal walls of the seat 22, the passage zone A s is absent, and the passage of the pressurized fluid from the second channel 5a towards the first channel 3a is prevented.

The movable seat 22 is bidirectionally movable according to the directions X and Y, parallel to the axis A. In particular, as it will be explained in more detail herein below, the movable seat 22 is moved along the direction Y by the pressurized fluid and it is moved along the direction X owing to the presence of a spring 25, arranged inside the movable seat 22 and acting on the latter.

In a non-illustrated embodiment, the spring 25 can be arranged outside the movable seat 22.

The end portion 34 of the piston 30 is received in a portion of the cavity 8 having substantially the same radial dimension. The end portion 34 has a maximum transverse dimension D P and comprises a piloting face 37 (Fig. 2). In use, the further pressurized fluid entering the valve 1 from the piloting opening 4 during the piloting step acts on the piloting face 37. The end portion 34 further comprises an annular face 47, which is frustoconical- shaped. The annular face 47 is opposite the piloting face 37 and it faces the intermediate portion 33. In the operative configuration K of the valve 1, the end portion 34 abuts on a shoulder 60 (shown in Fig. 2) of the cavity 8 and the connecting portion 52 contacts the seat 22. On the outer side wall of the end portion 34, a groove is made, which acts as a seat for a third sealing member 35, for example, an O-ring.

As it is apparent from Fig. 3, the piloting face 37 has the maximum transverse dimension Dp that is greater than the internal maximum transverse dimension Ds of the internal wall 22a of the movable seat 22. Since the movable seat 22 is interposed between the connecting portion 52 and the end portion 34 of the piston 30, the latter comprises a first part 30a and a second part 30b joined together, for example through a threaded connection (Figures 1 and 2). In this manner, since the internal maximum transverse dimension D s is less than both the radial extension of the connecting portion 52, and the maximum transverse dimension Dp of the piloting face 37, it is possible to correctly assembly the valve 1 by arranging the seat 22 and the piston 30 in the manner shown in the Figs. 1-3. By way of example, during the assembling, the first part 30a is first positioned by inserting the head portion 32 inside the containing element 16, then the movable seat 22 and the spring 25 are positioned, finally the second part 30b is positioned, which is screwed to the first part 30a.

The fact that the maximum transverse dimension D P is greater than the internal maximum transverse dimension Ds causes the pressurized fluid entering the valve 1 through the second channel 5a to exert on the piston 30 a thrust force F s (illustrated by an arrow in Fig. 3), which is oriented so as to push the piston 30 in the direction Y.

The safety valve 10, of a known type, is a maximum pressure valve detecting the fluid pressure in the second channel 5a (i.e., of the fluid arriving near to the intermediate zone 33) and it opens if the above-mentioned pressure exceeds a predetermined threshold value. The latter is a value set by the used acting on adjustment means with which the safety valve 10 is provided, and it can be equal to 350 bars. When the pressurized fluid in the second channel 5a exceeds this threshold value, the safety valve 10 opens, and a portion of the above-mentioned fluid enters the connection channel 26 to subsequently reach the piloting channel 4a. In the latter, the above-mentioned portion of the fluid traverses the dowel 6, with consequent pressure drop in the fluid. The pressure difference between the fluid upstream of the dowel 6 and the fluid downstream of the dowel 6 causes the piloting step to start. Consequently, the piston 30 moves in the direction of the arrow X and the pressurized fluid can leave the second channel 5a - so that the fluid pressure lowers below the threshold value - to reach the first channel 3a. In this case, the piloting step is not controlled by the operator, but it is automatically started by the valve 1 owing to the presence of the safety valve 10.

The operation of the valve 1 is described herein below, with particular reference to the case in which the latter is comprised in an earthmoving machine.

When a load has to be lifted, the pressurized fluid, for example an oil provided with suitable chemical-physical characteristics, enters the valve 1 through the first opening 3 communicating with the cavity 8 through the first channel 3 a.

The pressurized fluid reaches the movable seat 22 and moves the latter in the direction Y, thus moving the seat 22 away from the end 21 of the containing element 16. This is due to the fluid high pressures, which are able to overcome the elastic force exerted of the spring 25 on the movable seat 22. Instead, when the fluid is absent, the spring 25 acts on the movable seat 22 maintaining the latter abutting on the second fhisto-conical zone 52b of the connecting portion 52 of the piston 30.

Then the pressurized fluid traverses the passage zone As and it can flow, inside the movable seat 22, towards the second channel 5a. Through the second opening 5, the fluid exits the body 2 and moves towards actuating means (not illustrated), which is comprised in the machine and which, in this manner, is actuated to lift the load.

When the load has to be lowered, the valve 1 is initially in the first operative configuration K and the pressurized fluid exiting from the actuating means enters the valve 1 through the second opening 5. The flow of this fluid causes the movable seat 22 to move in the direction X until abutting on the end 21 of the containing element 16 (Fig. 2).

At the same time, through the piloting opening 4, a volume of further pressurized fluid enters the body 2 and flows in the piloting channel 4a. This fluid exerts a thrust action - i.e., a piloting force Fp represented by an arrow in Fig. 3 - on the piston 30, particularly on the end portion 34 of the latter. The piston 30 begins to move in the direction X so that the second fhisto-conical zone 52b moves away from the internal wall 22a.

Then the piston 30 moves inwards the containing element 16, so that the connecting portion 52 does not abut anymore on the end 21 of the containing element 16. In this manner, between the movable seat 22 and the piston 30, the passage zone As is defined, and the half-circular passages made in the end 21 are not closed by the connecting portion 52 anymore. The pressurized fluid entering from the second opening 5 can thus traversing the passage zone A s and the above-mentioned half-circular passages - after flowing in the second channel 5a and a portion of the first cavity 8 (inside the seat 22) - to exit subsequently the body 2 of the valve 1 through the first opening 3. When the lowering of the load has to be stopped, the further pressurized fluid is no more supplied to the piloting opening 4.

The piston 30 is then moved in the direction Y by the thrust action of the spring 41 , the elastic force F EL of which is not opposed anymore by the piloting force F P due to the pressurized fluid in the piloting channel 4a. In this manner, the connecting portion 52 of the piston 30 abuts again on the end 21 of the containing element 16 and the frusto-conical second zone 52b is in contact with the movable seat 22, thus interrupting the connection between the first opening 3 and the second opening 5.

In Fig. 3, the elastic force F E L, the thrust force Fs, and the piloting force Fp, are shown, all of which being substantially parallel to the longitudinal axis A. The elastic force FE L and the thrust force Fs are concordant and push the piston 30 in the direction Y, while the piloting force F P , opposite the other two, pushes the piston 30 in the direction X.

On the contrary, in the known valves, the thrust force Fs and the piloting force Fp are concordant and push the piston 30 in the direction X, while the elastic force FEL, opposite the other two, pushes the piston 30 in the direction Y.

Therefore, on the contrary of the known valves, in the valve 1 according to the invention the thrust force Fs opposes the piloting force F P .

In fact, the pressurized fluid entering the second channel 5a is distributed in the valve 1 so that it acts on both the annular face 47 of the end portion 34, and on a portion 46 of the frusto-conical second zone 52b positioned inside the seat 22 when the valve 1 is in the operative configuration K (Fig. 3), i.e., when the connecting portion 52 contacts the seat 22.

Since the maximum transverse dimension D P is greater than the internal maximum transverse dimension Ds, the area of the annular face 47 is greater than the area of the portion 46, and therefore the resulting thrust force F s is directed so as to oppose the piloting force Fp.

In the case when the spring 41 does not act anymore on the piston 30, for example due to an accidental breaking of one or more coils of the spring, and the force F E L thus becomes null, the valve 1 closure is ensured by the thrust force Fs that continues to oppose the piloting force Fp (an effect that cannot be obtained in the known valves). Owing to this, the piston 30 can move in the direction Y so as to contact the movable seat 22 and to stop the lowering of the suspended load. Moreover, this orientation of the thrust force Fs avoids that, when there are very high pressures of the fluid entering the valve from the actuating means (which typically occurs when the suspended load is very inclined), the load moves very quickly. In fact, even if the fluid pressures are very high, the thrust force Fs tends in any case to push the piston 30 in the direction Y, thus preventing the passage zone As from being excessively large. Therefore, owing to the thrust force Fs orientation, the valve 1 is able to adjust the flow rate of the pressurized fluid entering the valve 1 through the second opening 5a and exiting the valve 1 through the first opening 3a, i.e., during the lowering step of the suspended load.

The valve 1 can be associated to any machine or apparatus, even different from an earthmoving machine.

Owing to the invention, a load-holding valve 1 is provided which allows blocking the movement of the suspended load (for example the arm of an earthmoving machine) in the case of a breakage of the spring 41.

Furthermore, owing to the invention, a load-holding valve 1 is provided in which it is possible to compensate for pressure increases of the fluid entering the valve from the actuating means (through the second channel 5a) to avoid corresponding speed increases during the lowering of the suspended load. This is achieved owing to the orientation of the force Fs that tends to push the piston 30 in the direction Y, so as to avoid that the passage zone As becomes excessively large, so as to adjust the flow rate of pressurized fluid entering the valve through the second opening 5 a and exiting the valve through the first opening 3 a. This adjustment of the fluid flow rate is automatically performed by the valve 1, as described above, and it is therefore an accurate and reliable adjustment of the fluid flow rate.

Furthermore, variations and/or additions to what has been disclosed above and/or to what has been shown in the attached drawings are possible.