EP0437717B1 - Seat valve - Google Patents

Abstract

The valve, esp. load maintenance valve, has a housing chamber (R), with a valve member (V), pressed by a spring (C) against a seat (O). A first pressure medium channel (K1) is connected to the valve seat and a second channel (K2), to the chamber. The valve member is loaded in opposite directions by the channel pressures. The chamber contains a relief device (E) for the spring closure pressure of the valve member. This is actuated by the pressure in the second channel and in the chamber. It reduces the closing pressure, by the amount, which presses the valve member surface (f) on to the valve seat.

Description

The invention relates to a seat valve of the type specified in the preamble of claim 1.

Such seat valves are known in practice by the types MV, MVS, MVE, MVP and DMV, assembly 4, from Heilmeier & Weinlein, 8 Munich 80, which have been sold for years. They are used as a pressure relief valve, as a safety valve, as a pressure reducing valve and the like. The pressure to be regulated is present in the first pressure medium channel, while the second pressure medium channel leads, for example, to a tank line. With the setting of the preload of the spring, the pressure limit is determined at which the valve member lifts off the valve seat and allows pressure medium to flow out. If the second pressure medium channel is depressurized or almost depressurized, the seat valve responds properly. However, if the pressure in the second pressure medium channel rises for some reason, for example because the second pressure medium channel is connected to a working line, the pressure in the second pressure medium channel is added to the closing force generated by the spring, so that the pressure limit at which the poppet valve responds increases in an uncontrolled manner. Especially when such seat valves are used as load holding valves, this is an undesirable disadvantage, which requires the consumer and the system to be designed in such a way that the pressure limit which rises when they are added is coped with. Basically, seat valves with their simple valve members are inexpensive, compact and reliable, so that efforts are made to use it for the widest possible range of applications. However, the aforementioned addition effect limits the number of possible uses for seat valves.

In a safety shuttle valve proposed in EP-A1-0 376 115 with an older seniority, an elimination device for the spring closing pressure is provided, which suddenly removes the spring closing pressure when the valve member is lifted from the valve seat, so that the valve member reaches a second seat and the connection is closed cordoned off a relief line. When the valve member is pressed onto the valve seat, the elimination device is ineffective because its piston is exposed to the pressure in the relief line on both sides. A pressure increase in the relief line adds up to the spring closing pressure when the valve member rests on the valve seat.

In a hydraulic lockable check valve known from DE-A1-34 02 110, the closing spring presses the valve member together with the load pressure onto the valve seat. A pressure compensation piston in a control chamber facing away from the closing spring is loaded in the opening direction of the valve member on a loading surface with the load pressure which is equal to the loading surface of the valve member exposed to the load pressure in the closing direction. In this way, the load pressure is compensated without affecting the closing force of the closing spring. The control force remains constant regardless of fluctuations in load pressure. The check valve does not respond to a set limit of the load pressure. A pressure increase in the Drain line acts on the valve member in the opening direction and changes the closing force.

The invention has for its object to improve a seat valve of the type mentioned so that the addition effect is avoided.

The object is achieved in a structurally simple manner with the features specified in the characterizing part of patent claim 1.

For structural and physical reasons, the effect of the pressure prevailing in the second pressure medium channel on the valve member pressed onto the valve seat cannot be avoided. However, by reducing the spring closing pressure, the hydraulic closing force on the valve member, which increases with increasing pressure, is compensated for or largely compensated for by the relief of the spring in such a way that the addition effect does not occur. The poppet valve responds independently or almost independently of the pressure in the second pressure medium channel. The structure of the seat valve remains simple and inexpensive because essentially all the components that have been customary to date are used. Only the reducing device that can be easily integrated into the seat valve is added. The range of possible uses of such seat valves is advantageously increased.

Although it is known from sheet 30 of a prospectus belonging to the state of the art from Fluid-Controls, a lowering brake check valve with the type designation 1 EXP 65 83, in which the influence of a variable pressure in the second pressure medium channel on the opening behavior of the valve is thereby eliminated is that the valve member as a complicated, large-scale and processing technology sophisticated differential sleeve piston is formed, which is used in a complex and large housing so that it is pressure balanced. Such complex valves are particularly useful for large flow rates because of their size. These valves cannot be compared to simple, small seat valves. Furthermore, the influence of the variable pressure in the second pressure medium channel is achieved by a special construction of the valve member and the housing without involving the spring.

An expedient and structurally simple embodiment is set out in claim 2. The piston can be accommodated with little structural effort in such a way that it automatically and mechanically relieves the spring, depending on the pressure prevailing in the second pressure medium channel, as the pressure presses the valve member onto the valve seat. In this way, the variable pressure in the second pressure medium channel increasingly takes over the function of the spring, which is at least largely released from this function by the reducing device at the same time.

The embodiment of claim 3 is expedient because the piston relieves the spring to the same extent as the pressure presses the valve member onto the valve seat. The seat valve always works as if the second pressure medium channel were depressurized.

As an alternative to this, the embodiment according to claim 4 can also be appropriate, because with this undersize of the piston, a residual force of the spring remains effective, which ensures the mechanical function of the seat valve. This measure is also important for a flawless Guiding and holding the valve member, which could otherwise carry out undesired own movements if the spring is quickly tensioned when the pressure in the second pressure medium channel increases.

A further, particularly expedient embodiment emerges from claim 5. The piston relieves the spring via the pull rod, which is attached to the spring abutment that engages the valve member.

The embodiment according to claim 6 is also structurally simple and streamlined because the piston is located away from the direct working area of the valve member and does not impair the flow.

With regard to the functional reliability and the simple and space-saving structure, the embodiment according to claim 7 is useful.

Another important thought is included in claim 8. The liquid barrier element ensures that water or other harmful media do not enter the cylinder chamber from the outside environment and impair the function of the piston. The liquid blocking element can be arranged in the cylinder chamber, between the cylinder chamber and the external environment in the housing of the seat valve or on the outer side of the housing of the seat valve. If the liquid blocking element is a porous insert, e.g. made of sintered material, then the air can pass freely in both directions, while liquid or other harmful media are retained.

A further advantageous embodiment with axial flow through the seat valve results from claim 9 forth. In this embodiment, the basic concept of already proven seat valves is retained. Only the insert needs to be structurally adapted and the piston attached to the pull rod.

Finally, the embodiment of claim 10 is advantageous because the seat valve here, in its function as a load-holding valve, meets the requirements which, on the one hand, concern the flow in both directions and, on the other hand, the exclusion of an accumulation effect. The reduction of pressure surges on the part of the consumer is of particular importance. The shock valve is provided for this purpose. However, it is necessary for the load holding valve to allow the pressure to be reduced to reach the shock valve without the accumulation effect. If a pressure surge occurs, then because of the reducing device for the spring of the valve member, the poppet valve responds at the set pressure limit and allows the pressure to the shock valve, regardless of how high the pressure in the second pressure medium channel is. Specifically in a slide control valve with a closed neutral position, the pressure medium between the seat valve and the slide control valve could not flow out, so that the valve member would remain closed with high force. The reducing device ensures, however, that the seat valve responds properly and the shock valve can reduce the pressure surge.

Fig. 1

eine Schemadarstellung eines konventionellen gattungsgemäßen Sitzventils, das mit den Nachteil des Aufaddierungs-Effektes behaftet ist,

Fig. 2

eine Schema eines erfindungsgemäß ausgebildeten Sitzventils ohne den schädlichen Aufaddierungs-Effekt,

Fig. 3

eine hydraulische Steuervorrichtung, in der ein erfindungsgemäßes Sitzventil als Lasthalteventil enthalten ist,

Fig. 4

einen Längsschnitt durch eine konkrete Ausführungsform eines Sitzventils mit Lasthaltefunktion, und

Fig. 5

eine weitere Ausführungsform, ähnlich der von Fig. 4.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

Fig. 1

1 shows a schematic representation of a conventional seat valve of the generic type, which has the disadvantage of the addition effect,

Fig. 2

1 shows a diagram of a seat valve designed according to the invention without the harmful addition effect,

Fig. 3

a hydraulic control device in which a seat valve according to the invention is contained as a load holding valve,

Fig. 4

a longitudinal section through a specific embodiment of a seat valve with load holding function, and

Fig. 5

a further embodiment, similar to that of FIG. 4.

A seat valve S of a conventional generic type according to FIG. 1 contains a valve seat O in a housing (not shown in more detail), onto which a valve member V is pressed by a spring C. A first pressure medium channel K1, which carries the pressure P, leads to the valve seat O. The spring C is arranged in a housing chamber R, to which a second pressure medium channel K2 is connected, which has a pressure p. A third pressure medium channel K3 branches off from the chamber R to a safety or shock valve B, which has a response pressure P ', which is, for example, greater than the normal pressure P. The valve seat O has a cross-sectional area f which corresponds to the area , on which the pressures P and p act in opposite directions on the valve member V.

The pressure value of P is determined by f and the force of the spring C, i.e. the pressure limit at which the seat valve S responds. If the pressure p is equal to zero, the valve member V is lifted off when the pressure P is reached. The pressure P remains limited to a value which corresponds to the force of the spring C. However, if for some reason p increases to a value greater than zero, this pressure acts on the surface f of the valve member in the closing direction in addition to the force of the spring C. This means that the poppet valve no longer responds at the set pressure P, but only at one higher pressure. This addition effect is not practical if P has to be observed.

The shock valve B is used, for example, to reduce a pressure surge in the pressure medium channel K2. The pressure surge is only properly degraded if p is zero. Then the valve member V lifts off at the pressure P and allows the shock valve to respond in a predetermined manner. However, if the pressure p is greater than zero for some reason, the valve member V does not lift off from the valve seat O at the pressure P, but only at a possibly higher pressure. The shock valve B does not respond in the predetermined manner.

In the case of a seat valve S1 shown schematically in FIG. 2 according to the invention, the aforementioned addition effect is eliminated in a structurally simple manner. The components corresponding to FIG. 1 have been given the same reference numerals in FIG. 2. In addition, the seat valve S1 contains a relief device E for the spring C which acts on the valve member V. In its simplest form, the relief device E consists of a piston T with an action surface f 'which corresponds to or only slightly deviates from the action surface of the valve member V. The piston T is arranged between the valve member V and the spring C, the spring C sitting in a secondary chamber R ', which is relieved of the atmosphere A.

This configuration ensures that the poppet valve S1 responds at the set pressure P regardless of the pressure p. If the pressure p is greater than zero, then the piston T is acted upon in the opening direction of the valve member V and the spring C is deformed and relieved in relation to the valve member V as the pressure p presses the valve member V onto the valve seat O in the closing direction.

The surface f 'of the piston T is expediently equal to the surface f of the valve member V or the valve seat O, so that the pressure p cannot have a disruptive effect. However, in order not to jeopardize the guidance of the valve member V in the simple construction of the seat valve S1, the acting area of the piston T can be smaller than the acting area f of the valve member V, e.g. at 10%.

If a shock valve B as in FIG. 1 is connected to the chamber R via the third pressure medium channel K3, this will come into effect regardless of the pressure p.

In Fig. 3, the seat valve S1 is integrated as a load holding valve LHV in a hydraulic control device. The control device contains a schematically indicated slide control valve D, preferably with the neutral position closed. The shock valve B indicated in Fig. 2 is incorporated into the slide control valve D so that it can establish a connection to the return. The slide control valve D is used to control a consumer Z, here for example a double-acting hydraulic cylinder, which has to move a load L. Two lines Z1 and Z2 connect the consumer Z to the slide control valve D. In the line Z1, the poppet valve S1 is arranged such that the consumer Z is connected to the valve seat O via the line Z1, while the slide control valve D is connected to the chamber R. is. The relief device E is contained in the seat valve S1. Furthermore, the seat valve S1 with a check valve G, expediently one Platelet check valve, which enables an unimpeded flow in the direction from the slide control valve D to the consumer Z. Furthermore, a hydraulic unlocking device F is provided for the seat valve S1, which acts on the valve member through the valve seat O and is acted upon by a pilot line H, which is connected to the line Z2.

The load L is held by the seat valve S1 up to a set pressure. If a pressure surge occurs, for example because the load L generates an additional force in the direction of the arrow, the excess pressure is reduced via the shock valve B. For controlled movement of the consumer Z to the left, pressure is built up in the line Z2 via the slide control valve D, which lifts the valve member V from the valve seat O via the auxiliary control line H and the unlocking device F so that a certain movement speed is maintained. To move the consumer Z against the load, the check valve G opens; the unlocking device F need not come into effect for this.

4 shows a more specific embodiment of the seat valve S1, again using the same reference numerals as in FIG. 2 for the corresponding elements.

The seat valve S1 has a sleeve-shaped housing 1 with an inner bore into which an insert 2 is screwed, which contains the second pressure medium channel K2 as an axial bore. Furthermore, a central bore 3 is made in the insert 2, which is closed at one end by a plug 4. From the Bore 3 leads a relief port 5 to the atmosphere, which is closed by a liquid blocking element 6. Furthermore, a rear spring abutment 7 is screwed into the housing 1, which supports the end 20 of the spring C, which is averted from the valve member V, here a helical spring 21, and allows the pretension to be changed. The other end 19 of the spring C is seated on a spring abutment 8, which stands on the valve member V designed as a ball 11. The spring abutment 8 is connected to a tie rod 9 which projects into the bore 3 and carries the piston T, 10 there. The piston T, 10 is sealed and displaceable in the bore 3, which defines a cylinder space 22 which is open to the chamber R.

At the lower end of the housing 1, a further housing part 12 is screwed, which contains the valve seat O designed as an insert 13. The check valve G arranged there is a plate valve, consisting of an annular disk-shaped plate 14 and through channels 15 in use 13. In the housing part 12, the unlocking device F is also housed, which has a piston 24 and a plunger 23, which through the valve seat O directly on the valve seat V attacks.

The check valve G opens in the direction of flow from the pressure medium channel K2 to the pressure medium channel K1; the pressure medium flows through relatively unthrottled. In the opposite direction, ie in the flow direction from the pressure medium channel K1 to the pressure medium channel K2, the check valve G. closes. The pressure from the pressure medium channel K1 must lift the valve member V from the valve seat O against the force of the spring C, whereby it is determined by the force of the spring C. Must reach pressure level if the unlocking device F is not is operated. On the other hand, if the unlocking device F opens the valve V, O, then pressure medium flows out to the extent that this is brought about by the actuation of the piston 24. The piston in each case is pressurized in the chamber R. Via the pull rod 9 and the spring abutment 8, it relieves the valve member V of the spring C to the extent that the pressure in the chamber R increases.

The alternative embodiment of the seat valve S1 according to FIG. 5, which in turn can be a load holding valve LHV, contains as the valve member V a cone 16 abutting the spring abutment 8 with a cylinder 17 immersed in the valve seat O, in which orifice openings 18 are provided. The insert 13 is here somewhat larger than in FIG. 4. The cylinder 17 with the orifice openings 18 leads to an improved control behavior of the seat valve S1. In further construction, the seat valve S1 corresponds to the seat valve S1 of Fig. 4, i.e. the pull rod 9 carries a piston acted upon by the pressure in the chamber R against the force of the spring C, the other side of which is relieved of the atmosphere.

Claims (10)

1. Seat valve (S1), in particular load retention valve, having a valve element (V) which can be pressed by a spring (C) against a circular valve seat (O) arranged in a chamber wall in a housing chamber (R), having a first pressure medium passage (K1) connected to the valve seat (O) and having a second pressure medium passage (K2) connected to the chamber (R), which pressure medium passages are separated from one another by the valve seat (O), whereby the valve element (V) can be subjected fully and in mutually opposed directions to the pressures in the pressure medium passages (K1, K2) over an area (f) determined by the diameter of the valve seat (O), characterised in that a reducing device (E) for the spring closing pressure of the valve element (V) is provided in the chamber (R), which reducing device (E) can be actuated when the valve element (V) is pressed onto the valve seat (O) by the pressure present in the second pressure medium passage (K2) and in the chamber (R), and by means of which reducing device (E), the spring closing pressure is reduced approximately to the extent that this pressure on the surface (f) of the valve element (V) presses the latter onto the valve seat (O).
2. Seat valve according to Claim 1, characterised in that one end (19) of the spring (C) acting on the valve element (V) is mechanically coupled to a displaceable piston (T, 10) sealed in the opening and closing direction of the valve element, which piston is subjected to the pressure in the second pressure medium passage (K2) in the opening direction of the valve element (V) and is subjected to atmospheric pressure in the closing direction of the valve element (V).
3. Seat valve according to Claim 2, characterised in that the area of the piston subjected to pressure is equal to the area (f) subjected to pressure of the valve element (V) on the valve seat (O).
4. Seat valve according to Claim 2, characterised in that the area of the piston subjected to pressure is smaller than the area (f) subjected to pressure of the valve element (V), preferably by approximately 10%.
5. Seat valve according to Claim 2, characterised in that the piston is attached to a tie rod (9) arranged within the spring (C) configured as a helical spring (21) and that the tie rod (9) is connected to a spring support (B) for the one spring end (19) acting on the valve element (V), the spring support (8) being in contact with the valve element (V).
6. Seat valve according to one of Claims 1 to 5, characterised in that the tie rod (9) passes through a spring support (7) for the other spring end (20), the spring support (7) being arranged in the chamber (R), and protrudes into a cylinder space (22) open towards the chamber (R), in which cylinder space (22) the piston can be displaced so that it is sealed and is relieved to atmosphere in the direction facing away from the chamber (R).
7. Seat valve according to one of Claims 1 to 6, characterised in that the valve element is spherical or conical.
8. Seat valve according to Claim 6, characterised in that a relief passage (5) of the cylinder space (22) is closed by an air-permeable liquid shut-off element (6), preferably by a soft O-ring with non-return function or by a porous insert, for example in sintered material.
9. Seat valve according to Claim 6, characterised in that one pressure medium passage (K2) is arranged in an insert (2) bounding the chamber (R), and in that the cylinder space (22) in this insert (2) is formed by a passage hole (3) closed at the end facing away from the chamber (R) by means of a plug (4).
10. Seat valve according to one of Claims 1 to 9, characterised in that the seat valve (S1) is configured as a load retention valve (LHV) through which flow occurs by means of the valve seat (O) in the flow direction from the first (K1) to the second pressure medium passage (K2) and by means of a parallel non-return valve (G) in the opposite flow direction, the load retention valve (LHV) having a reset device (F) acting through the valve seat (O) on the valve element (V), and is arranged, in a hydraulic control device in a conduit (Z1) between a consumer unit (Z) and a spool control valve (D) connected to the pressure medium supply, in such a way that the first pressure medium passage (K1) connected to the valve seat (O) is connected to the spool control valve (D), which is preferably closed in the neutral position, the second pressure medium passage (K2) being, on the other hand, connected to the consumer unit (Z), that the reset device (F) is connected to a further consumer unit conduit (Z2), and that a shock valve (B) is arranged, preferably in the spool control valve (D), for the conduit (Z1) containing the load retention valve.

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