GB2259968A

GB2259968A - Double-seat valve device

Info

Publication number: GB2259968A
Application number: GB9218745A
Authority: GB
Inventors: Helmut Goettling; Rudolf Moeller; Gerhard Scharnowski
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1991-09-04
Filing date: 1992-09-04
Publication date: 1993-03-31
Also published as: ITMI921738A0; DE4129755C2; ITMI921738A1; IT1255434B; GB9218745D0; FR2680852A1; DE4129755A1

Abstract

A double-seat valve device comprises a valve housing within which is located at least one valve tappet 2 with two valve discs 3, 4 coupled thereto, each of which, in a closed state, is pressed against a valve seat to form a space 10 therebetween connectable to a first pressure medium line P. The space, upon actuation of the valve tappet to simultaneously raise the valve discs from the valve seats 5, 6 is connected to at least a region of the remaining interior 11 of the valve housing which, in turn, is connectable to a second pressure medium line A. An actuating cylinder comprising a piston 7, a cylinder space 13 and a control pressure medium line 9 which opens into the cylinder space is provided for valve tappet actuation. The interior region 11 of the housing, which is connectable to the second pressure medium line A, has a constant pressure-medium connection to the entire cylinder space provided by clearances around the tappet 2 and the piston 7. <IMAGE>

Description

? 21" C^ (I P DOUBLE-SEAT VALVE DEVICE The invention relates to a

double-seat valve device.

one known double-seat valve device is described in German Patent 2837298. This known double-seat valve device consists of a valve tappet with two valve discs arranged one behind the other thereon which are movable relative to one another, whereby one of the valve discs can be positioned against the other during the opening operation after the tappet has moved a predetermined distance, and forms therewith a cavity from. which a seepage line leads through the valve tappet and out of the housing. The valve discs are fixed to the tappet but one of the valve discs is rigid and the other valve disc is elastic. If the tappet is actuated, the rigid valve disc lifts away from its valve seat. The other valve disc, however, is so elastic that its sealing circumference remains on its valve seat even after the rigid valve disc has been lifted away until the rigid valve disc comes to rest on it and forms a cavity therewith. This cavity leads into the seepage line. A further displacement of the tappet then causes the elastic valve disc to lift from its valve seat whereby the valve is opened. The opened valve defines a large opening crosssection or a large nominal width. However, a disadvantage of this valve arrangement is that the forces of the pressure medium, which is to be switched, are transmitted via the valve discs to the valve tappet in such a way that the drive of the tappet has to absorb them. This means that either the drive for the tappet has to operate against the pressure of the pressure medium, or, the pressure of the pressure medium tends to lift the valve discs away in the opening direction, so that additional locking of the tappet in the closed position is necessary.

This problem occurs in many double-seat valve devices known hitherto which have large nominal widths, since, as in the abovedescribed double- seat valve, the valve discs are displaced in or counter to the direction of flow of the pressure medium which is to be switched, and thus the entire pressure of the pressure medium acts on the valve discs.

2 A valve is known from European Patent Application 0096751 in which the pressure medium lines open into the housing laterally, i.e. perpendicular to the direction of displacement of the valve tappet. The valve tappet is formed with regions of differing cross-section. Sealing of the pressure medium lines from one another is produced by bearing of a thickened region against the walls of the guide bore. Connection of the pressure medium lines is produced by changing the tappet position to locate a thinner region within the guide bore. The geometry of the tappet, which, so to speak, incorporates the valve discs, and also the guidance of the pressure medium lines, mean that the valve tappet can be moved relatively independently of the pressure due to the pressure medium. However, a disadvantage is that the arrangement is not suitable for large nominal widths.

Another double-seat valve device is known from German Patent 2934181. This known valve arrangement comprises 'two valve seats arranged coaxially in a valve housing and an axially displaceable valve tappet which is connected to two valve discs which can be closed on to the corresponding valve seats. In the closed state, the two valve discs which are closed on to the valve seats form a space into which a first pressure medium line opens. When the valve tappet is actuated, this space is connected to the remaining interior of the valve housing around the space, the remaining interior being connected to a second pressure medium line. Thus, if the valve tappet is actuated, a pressure medium-through connection is produced between the first and the second pressure medium lines. When the valve tappet is actuated, both the valve discs lift away from the valve seats simultaneously so that a large throughput cross- section is released. The valve tappet itself is actuated by means of an electromagnet. However, a disadvantage of this arrangement is that, when the valve is actuated, a large cross-section is released immediately, i.e. abruptly, and, when closed, the passage 3 is blocked abruptly.

It is an object of the invention to provide a double-seat valve arrangement in which the valve tappet can be actuated with low displacement forces, which has high operating reliability and a configuration.

simple and compact A doubleseat valve device, in accordance with the invention, comprises a valve housing within which is located at least one valve tappet with two valve discs coupled thereto, each of which, in a closed state, is pressed against a valve seat to form a space therebetween connectable to a first pressure medium line, which space, upon valve tappet actuation to simultaneously raise the valve discs from the valve seats is connected to at least a region of the remaining interior of the valve housing which is connectable to a second pressure medium line, wherein an actuating cylinder comprising a piston, a cylinder space and a control pressure medium line which opens into the cylinder space is provided for valve tappet actuation, and wherein the interior region which is connectable to the second pressure medium line has a constant pressure-medium connection to the entire cylinder space.

The doubleseat device has a number of advantages. The fact that the cylinder space of the actuating, or working, cylinder has a pressureinedium connection to the housing interior region which is connectable to the second pressure medium line means that the pressure medium required for actuating the working cylinder communicates with the pressure medium lines which are to be switched. This has a very extensive and advantageous effect on operation and furthermore on the simple configuration of the valve. The communication thus brought about of the control pressure medium line with the pressure medium lines which are to be switched results in the switching of the pressure medium lines taking place in a damped manner. This operation will be described in greater detail below.

4 In a preferred embodiment, the pressure-medium connection is provided by a corresponding play or clearance in the region of the elements of the actuating cylinder. Said play may, for instance, simply be achieved by dispensing with sealing elements in the region of the piston. This applies likewise to the opening between the actuating cylinder and valve housing interior, through which the valve tappet passes, which therefore allows passage of the pressure medium. Due to the reduction in friction which this involves, a further reduction in the necessary valve regulating forces is produced.

The arrangement of two valve discs connected to a tappet and two valve seats arranged correspondingly in the housing, which seats in one special configuration have the same internal widths, whereby both valve discs are able to be lifted away or closed simultaneously, and one of the pressure medium lines to be switched opening into the space formed between the valve discs in the closed state, leads to the pressure of the pressure medium acting on the two valve discs being such that the forces caused thereby act oppositely in the axial direction of the valve tappet. That is to say that the fact that the internal widths of the valve seats are thesame size means that the forces exerted on both valve discs are not only opposite but also equal. The valve tappet and hence also the drive therefor are pressurerelieved or pressure-compensated. This leads to the advantage that low valve forces are sufficient to actuate the valve, even at high pressures. There-fore, the valve discs or the valve seats may be made of large crosssection, whereby a large cross-section for connectingthrough the pressure medium is possible.

The combination of advantages, i.e. the large nominal width with simultaneous low valve regulating forces and the damped switching of the pressure medium paths, means that the double-seat valve device is universally usable and ensures high operating reliability.

In order that the simultaneous raising or closing 1 j capability of the valve discs away from or on to the valve seats is ensured and constantly readjustable, in an advantageous configuration, one of the valve seats or one of the valve discs is axially displaceable or adjustable relative to the valve tappet.

In an advantageous configuration, the pressure medium line which opens into the space formed between the valve discs in the closed state is the main pressure medium line, which permanently bears the pressure of the pressure medium. The remaining space within the valve housing is then connected with the working line in a simple manner.

A control pressure medium line opens into the actuating cylinder space on the side of the piston remote from the valve tappet. The fact that the piston and the valve tappet are provided with a play means that, when the actuating cylinder is acted upon via the control pressure medium line, the medium flows around the piston due to the play and can then penetrate further through the opening and into the rest of the interior of the valve housing, and thus also into the working line. This has the advantage that when the vale is actuated, i.e. when pressure acts on the control pressure medium line, the control pressure medium ventilates the working line until the piston moves and lifts the valve discs away and thus connects the main pressure medium line to the working line. This achieves a so-called damped switch-on action. This damped switchingon is provided, as a result of the design of the doubleseat valve device in a structurally very simple but effective manner. The clearance provided between the actuating piston and cylinder and between the valve tappet and opening can be defined such that, upon production of' the individual parts with appropriate dimensional tolerances, they cannot overlap. The clearance produced in the assembled state can additionally be achieved, for instance, by omitting the usual seals on the piston or on the valve tappet. Such omission of seals, to form the clearance, furthermore leads to an additional reduction in 6 the necessary valve tappet actuation force. This means that in an advantageously simple manner it is possible for low control pressures to connect the valve through reliably irrespective of the pressure of the pressure-medium in the lines to be switched. This reduced friction furthermore completely avoids the so-called stickslip behaviour which is typical of known valves, and a minimum mechanical hysteresis is produced.

The configuration of the double-seat valve device is not only such that low adjusting forces are sufficient to actuate the valve, but also simultaneous flow of medium about the working piston on actuation is ensured whereby a damped switch-on effect is achieved. The valve will operate as a continuous valve with high dynamics and in addition, is inexpensive to construct.

Preferably a spring is connected to the valve tappet and acts in the closing direction to keep the valve closed in the non-actuated state. The dimensions of this spring may be small since the entire valve is pressurecompensated. In other words, this means that even with large applied pressures due to the pressure medium, a spring having a relatively low spring force can keep the valve closed.

These advantages are yielded both for a configuration in which one valve tappet with two valve discs and two valve seats are located within a valve housing and for a configuration as a 3/3-way valve with two valve tappets within a valve housing.

In this further possible configuration of the double-seat valve device to form a 3/3-way valve, two valve tappets are provided each with two valve discs and the housing is correspondingly arranged with two valve seats each per valve tappet. This valve arrangement is constructed such that the main pressure medium line opens between the valve seats or the valve discs of one valve tappet and the vent line opens between the valve seats or valve discs of the other valve tappet, and that the 11 :1 7 remaining interior regions within the valve housing which are f ormed in the closed state are connected to one another and open into the working line. This provides a 3/3-way valve which releases a large cross-section both in the ventilation and venting region. This permits a high throughflow rate and reliable and rapid switching of high quantities of pressure medium. In this case as well, the respective drive means for the two valve tappets is designed as an actuation cylinder and likewise a clearance is provided between the pistons and walls of the actuation cylinder and between the tappets and the openings through which they pass to provide a pressure-medium connection between the actuating cylinder and the interior of the valve housing. In an advantageous configuration, the two valve tappets are matched to one another with respect to their valve seats such that, when there are displacement forces on both actuating pistons running in parallel and in the same direction, one of the valve tappets lifts the valve discs away from the vale seats and the other valve tappet urges the valve discs harder against the valve seats. This yields two partial valves, one valve acting as a ventilation valve and the other partial valve as a vent valve. The valve action in opposite directions with displacement forces running in parallel and in the same direction causes, for instance when opening the ventilation part of the valve arrangement, the main pressure medium line to be connected through into the working line and the venting part of the valve arrangement to be sealed more strongly. Since both valve tappets are provided with springs acting in the closing direction, the closing action for both valve tappets or the respective discs is promoted thereby. The integration of the entire valve elements, which virtually represent two valves in a common housing, is provided in a simple, expedient and inexpensive manner.

The clearances in particular in the region of the openings which allow the tappets through and which then open into the working line, mean firstly that the control 8 line of the actuating cylinders can also be vented and secondly that the actuating pistons driving the valve tappets can be acted upon by pressure, and thus be displaced, in both directions. A common pressure medium control line may open into both cylinder spaces of the actuating cylinder which results in both valve tappets always being acted upon at the same time. As already explained above, this means that when one of the partial valves opens the other closes simultaneously.

Upon ventilation of the control line, the piston surfaces of the two working cylinders are acted upon simultaneously. The tappet switching the main pressure medium line, i.e. the ventilation tappet, opens and the venting tappet is closed with the force F P - A (A = piston surface) in addition to the spring force.

Control pressure medium additionally flows via the unsealed piston into the working line and promotes the ventilation.

This then leads to the afore-mentioned action of damped ventilation of the working line. In order to keep the valve arrangement open, it is necessary for the control pressure to be greater than the working pressure.

For venting, the control line is opened. The pressure across both pistons drops, and the ventilation tappet is closed with the force F = P. A in addition to the spring force. The venting tappet on the other hand opens and vents the working line, since the pressure in the working line actuates the underside of the piston via the clearances and correspondingly opens this venting tappet against the spring force. Additionally working line pressure medium flows across the unsealed piston and promotes venting.

The invention will now be further described by way of example only with reference to the accompanying drawings in which:- Figure 1 shows a double-seat valve arrangement with A 9 one valve tappet; and Figure 2 shows a double-seat valve arrangement with two valve tappets as a 3/3-way doubleseat valve.

Figure 1 shows a double-valve arrangement with a valve tappet 2 and two valve discs 3, 4 and valve seats 5, 6 respectively. The double-seat valve is shown in the closed state. in this state, both valve discs 3, 4 lie in sealing fashion on the corresponding valve seats 5, 6 and form a space 10 into which the main pressure medium line P opens. The space 11 within the valve housing 1 remaining around tChis space 10 then opens into the working line A.

A cylinder space 13 is also provided which effectively opens into the working line A as well via the play between piston 7 and the cylinder walls and between the valve tappet 2 and through opening 8.

The main pressure medium line P opens into the space 10 formed between the valve discs 3, 4 in the closed state. Due to the fact that both valve seats 5, 6 have the sane internal width, the pressure of the upper and lower valve discs exerted on the valve discs 3, 4 is of the same amount. The forces brought about by the pressure, however, are opposed, so that they cancel each other out altogether. This means that the valve tappet 2 in the region of actuation is force-free. closing direction, can A spring 12, which acts in the thus keep the valve closed independently of the pressure in the main pressure medium line. The valve discs 3, 4 and also the valve seats 5, 6 are aligned such that both valve discs 3, 4 lift away from the valve seats 5, 6 in the same direction due to displacement of the valve tappet 2 downwards.

If the control line 9 is supplied with pressure, control pressure medium first flows around the working piston 7, and then on through the clearance provided between the valve tappet 2 and opening 8 and into the working line A, and the working line A is initially ventilated in damped manner. At the same time, however, sectional pistons 7, the control pressure medium produces a downwards displacement of piston 7 even while f lowing therearound, which means that both valve discs 3, 4 are lifted away from the valve seats 5, 6 against the spring 12. This takes place simultaneously since in the assembled and set state the valve discs 3, 4 are rigidly coupled to the valve tappet 2. "Setting" here means that one of the valve seats 5, 6 or one of the valve discs 3, 4 can be displaced and then fixed in the axial direction. This ensures that both valve discs lift away from the valve seats simultaneously, independently of the production tolerances achieved. Once the valve tappet 2 is displaced downwards and the valve discs 3, 4 are both lifted away from the valve seats 5, 6, the pressure medium then flows upwards out of the previously closed space 10 and downwards into the actuating or working line A. What is important in this case is that the pressure of the control pressure medium is greater than the pressure in the working line A, since otherwise displacement of the working piston 7 downwards would not be possible. If the control line 9 is then vented, the spring 12 causes the valve tappet 2 to be pushed upwards again and the valve discs 3, 4 to close on the valve seats 5, 6. At the same time, the working line A can then vent via the clearances between the valve tappet 2 and opening 8 and working piston 7 and working cylinder walls 13 via the control line 9.

Figure 2 shows a 3/3-way double-seat valve. In this representation, the arrangements of the 71, the cylinder spaces 13, 131, the pressure medium lines and housing recesses and also the valve seats 541 51 6, 6' and valve discs 3, 31, 4, 41 with tappets 2, 21 and the arrangement of the springs 12, 12/ can be seen. Each of the valve tappets 2, 21, valve discs 3, 31, 4, 41, valve seats 5, 51, 6, 61, corresponding spring element 12, 12' and the housing elements guiding the pressure medium lines are constructed as in Figure 1. The interconnection of two valve tappets 2, 2' with corresponding drive A zm 11 elements 7, 71, 13, 13', valve discs and valve seats shown in this figure is however specially designed to form a 3/3way valve.

The drive element 7, 71, 13, 131 of each valve tappet 2, 21 in this case also consists of a working cylinder 13, 131 in which seals are dispensed with both in the piston 7, 71 and in the respective valve tappet 2, 2' which is passed through the corresponding opening 8, V. This provides the corresponding clearance. The valve tappet 2 in the left-hand part of the figure serves to ventilate the working line A. The valve tappet 21 in the right-hand half of the figure of the valve arrangement serves to vent the working line A. In the left-hand part of the figure, the valve tappet 2 is-connected to the valve discs 3, 4 and the valve seats 5, 6 are matched to one another such that upon displacement downwards the two valve discs 3, 4 connected to this valve tappet 2 lift away from the valve seats 5, 6 simultaneously and in the same direction and release the space 10 formed between the valve discs 3, 4 of this valve tappet 2 when in the closed state. The main pressure-medium line P opens into this space 10 formed in the closed state by these two valve discs 3, 4 and acts upon this space in the closed state as well with the pressure medium of corresponding pressure. In the opened state, connect ingthrough is then performed both downwards and upwards by lifting both valve discs 3, 4. Since the remaining space 11 within the valve housing i opens into the working line A, a passage for the pressure medium from the main pressure medium line P into the working line A both downwards and upwards is provided. Such opening of the valve elements is brought about by acting on the pistons with pressure medium via the control line. If a pressure is applied in the control line 9, the piston 7 moves in the left-hand half of the picture such that the tappet lifts the valve discs 3, 4 away from the valve seats 5, 6 and opens the valve. Since the control air also penetrates into the working line via the 12 clearances in the piston and tappet region before opening or lifting away the valve discs, the ventilation of the working line is thus supported, and here too a virtually damped switch-on ventilation is produced. Upon the movement of the valve tappet 2 downwards, i.e. in the opening direction, the left-hand working piston 7 acts against the helical spring 12 located on the lefthand valve tappet 2, which spring acts as a pressure spring. Since the valve discs 3, 4 of the left-hand valve tappet 2 enclose the space 10 into which the main pressure medium line P opens and in the opened state release this space 10 both upwards and downwards, the valve tappet 2 is completely pres sure- comp ens ated in this case too. This means that when the valve is opened it is not necessary to operate against the pressure or the pressure difference of the pressure medium lines. The valve can likewise not open automatically, since even when there is a corresponding pressure in the main pressure medium line P the forces caused thereby on the valve discs of the valve tappet are antiparallel and of identical amounts, and thus cancel each other out. This cancellation of the forces is provided as in the valve of Fig. 1. However, the actuation of' the valve takes place only as long as the pressure in the control line 9 is greater than the pressure in the working line A, since the pressure in the working line penetrates from the piston side opposed to the control line through the clearance of the opening 8 around the valve tappet 2, and directs a corresponding counter- force onto the piston. However, the clearances are calculated such that even when the pressure medium flows over from the control line into the working line a pressure drop is always retained in the actuated state, so that the valve tappet remains correspondingly actuated.

The general view, i.e. both the left-hand and righthand halves of the figure, altogether represents the integration of two valves to form a 3/3way valve. Only the arrangement of the valve seats and the corresponding z 13 orientation of the valve discs differ in the right-hand half of the figure from the valve of the left-hand half of the figure. This leads to functional cooperation in a 3/3 way valve in a very advantageous manner. If the control line 9 is supplied with pressure, both working pistons 7, 7,1, i.e. the right-hand and left-hand working pistons, are subjected to the action of force in the same direction. This leads to the left-hand working piston 7 being displaced downwards, opening the corresponding valve discs, and switching the main pressure medium line P into the working line A. At the same time, a downward force likewise acts on the right-hand working piston -1 1, but this leads to increased pressing of the two valve discs 31, 41 on to the corresponding valve seats 5 1, 61 due to the correspondingly opposed orientation of valve disc 31. 4/ and valve seats 51, 61. This means that when the left-hand valve connects through for ventilation, the other valve is more firmly closed and undesirable venting of the working line is prevented. The helical spring 121, which is located on the right-hand valve tappet 21 and likewise acts as a pressure spring, in the non-actuated state causes the vent line R likewise to be kept closed in any case, even if only by spring force. If the pressure in the control line 9 then drops, for instance due to intentional switching-off of the control pressure medium, the force acting on the control line-side piston surfaces drops to zero and the pressure medium in the working line A penetrates through the clearance of the opening 8, 81 to the underside of both working pistons 7, 71, so that both working pistons are moved upwards. This causes the left-hand valve tappet 2 to close the valve discs 3, 4 on to the valve seats 5, 6, and the right-hand valve tappet 21 to lift the valve discs 31, 41 away from the valve seats 51, 61 and to release the working line A into the vent line R. The working line is then vented through the vent line R, the venting operation beginning as soon as the pressure of the control pressure medium drops via the leakage points of the two openings 8, 14 81 and also of the untight working piston 7, 71. This causes the venting operation as well to take place in damped manner to a certain extent.

This double-seat valve arrangement can be used as expediently and effectively both when using a single valve, i.e. a single tappet with correspondingly two valve discs and valve seats and one working piston, as with a 3/3-way double -seat valve. The coupling of both valves in a 3/3way valve is therefore advantageous because the working pistons are provided with a common control line and likewise the working line and the openings which open therein for both valve tappets are already suited identically to functional cooperation in a multiple arrangement of valves. only the main pressure medium line P and the vent line R are associated with the corresponding valve tappet or the valve discs and valve seats. Altogether, a simple integration is produced, and also an effective and in addition inexpensive structural form by dispensing with sealing elements. However, the virtually unsealed pistons could also be replaced by correspondingly sealed pistons, in which case care must simply be taken that the openings which allow-the valve tappets through provide sufficient play for pressure medium to act on the piston surfaces on the valve tappet side. Another possible configuration would be to dispense with actuating pistons entirely and to actuate the valve tappets via membranes or corrugated tubes. In this case, it is likewise important that both membrane sides or corrugated tube sides, i.e. both on the control line side and on the valve tappet side, can be acted on by pressure medium in order to permit a movement in both directions for the purpose of opening and closing the valve. This valve arrangement is particularly suitable for use, i.e. for joint use of pilot controls, due to the arrangement of the control line. Finally low actuating forces are necessary but simultaneously large pneumatic nominal widths are possible.

The feature of providing a pressure-medium connection between the entire cylinder space of the working cylinder and the interior of the valve canalso be realised in that the opening which allows the valve tappet through and is likewise pressuremedium-permeable can be omitted, i.e. virtually widened to such an extent that a partition between the cylinder space and the interior of the valve housing no longer exists. This means that the cylinder space of the working cylinder opens openly into the interior of the valve housing and hence into the working line. What is important in this case is only that, as before, the working piston, in whichever form, is permeable to pressure medium; i.e. that there is a pressure-medium connection between the control line and the working line.

Furthermore, it is also important to mention that in order to ensure the pressure-medium connection between the interior of the valve and the cylinder spaces, the pressure medium for which the valve is intended should be taken into consideration. If the valve is intended to switch gaseous pressure medium, for instance compressed air, and also to be operated by means of compressed air, the clearance in the region of the working piston and in the region of the opening which allows the valve tappet through may be of smaller dimensions than for use as a hydraulic valve. This means that the viscosity of the pressure medium must also be taken into account in the production of the pressuremedium connection between the interior of the valve and the cylinder space of the working cylinder.

16

Claims

1. A doubleseat valve device comprising a valve housing within which is located at least one valve tappet with two valve discs coupled thereto, each of which, in a closed state, is pressed against a valve seat to form a space therebetween connectable to a first pressure medium line, which space, upon valve tappet actuation to simultaneously raise the valve discs from the valve seats is connected to at least a region of the remaining interior of the valve housing which is connectable to a second pressure medium line, wherein an actuating cylinder comprising a piston, a cylinder space and a control pressure medium line which opens into the cylinder space is provided fcr valve tappet actuation,- and wherein the interior region which is connectable to the second pressure medium line has a constant pressure-medium connection to the entire cylinder space.

2. A double-seat valve device as claimed in claim 1, wherein the main pressure medium line opens into the space formed between the valve discs in the closed state thereof, and the working line opens into the interior region of the valve housing.

3. in Claim 1, wherein two valve tappets each with an actuating cylinder are provided to form. a 3/3-way doubleseat valve, the valve tappets being arranged parallel and adjacent to one another within the valve housing such that, when the valve tappets are actuated in the same direction, one valve tappet lifts the valve discs coupled thereto away from the' associated valve seats while the other valve tappet urges the valve discs coupled thereto harder against the associated valve seats.

A double-seat valve device arrangement as claimed

4. A double-seat valve device as claimed in Claim 3, wherein the main pressure medium line opens into the space 17 formed between the valve discs coupled to one valve tappet in the closed state thereof, and a third pressure medium line which forms a vent line opens into the space formed between the valve discs of the other valve tappet in the closed state thereof, and the working line opens jointly into the interior of the housing remaining around both spaces.

5. A double-seat valve device as claimed in any preceding Claim, wherein the cylinder space(s) of the actuating cylinder(s) is integrated into the valve housing and is connected to the interior of the valve housing by an opening, through which opening(s) pressure medium and the valve tappet(s) can pass, and wherein the piston(s) have a clearance for the passage of pressure medium.

6. A double-seat valve device as claimed In any preceding claim, wherein a fourth pressure medium line which acts as a common control pressure medium line opens into the cylinder space(s) of the actuating cylinder(s) on the side of the working piston(s) which is remote from the valve tappet(s).

7. A double-seat valve device as claimed in any preceding Claim, wherein one of the valve discs or one of the valve seats of the or each valve tappet is axially adjustable relative to the valve tappet.

8. A double-seat valve device as claimed in any preceding Claim, wherein the or each valve tappet is provided with a spring which acts thereon in a valve closing direction.

9. A double-seat valve device as claimed in any preceding Claim, wherein the valve seats coupled to the or each valve tappet have the same internal widths.

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10. A double-seat valve device substantially as hereinbefore described and illustrated in the accompanying drawings.

v, j:

11