SAFETY VALVE

Description

Technical field

[0001] The invention relates to a safety valve for control tasks with high pressures and flows. State of the art

[0002] For fluidic control tasks with high pressures and flow rates, there are operational safety requirements that arise, for example, from the safety-specific standard EN ISO 13849. In practice, such requirements exist, for example, in the stretch blow molding of containers made of glass or PET with pressures of up to 40 bar. Relevant safety functions here include preventing the unexpected start-up of a machine or system, as well as an energy dissipation function for safely isolating or relieving the machine or system of energy. In fluid technology, suitable redundant valves are used as safety-related parts of the control system, so that a single fault in one of these parts does not lead to the loss of the safety function. Such redundant orDual-channel structures, often in conjunction with sensory condition monitoring to detect individual faults and a suitable control system, achieve higher categories and performance levels as defined by the standard and minimize the probability of dangerous failures that can result, for example, in unexpected machine movements or noise emissions. Particularly in applications with high pressures, the protection of downstream system elements from damage caused by sudden pressure increases is also important. Sensory condition monitoring in this context includes, for example, proximity switches or pressure sensors to detect individual faults based on, for example, the position of the valve tappets or the pressure level in certain valve areas.

[0003] State-of-the-art integrated pneumatic safety valve solutions for low-pressure applications using slide valves are known. These solutions prevent unexpected start-up and ensure the safe de-energization or venting of machine components through redundant valve functions. However, these solutions are not suitable for pneumatic control tasks with high pressures and flow rates.

[0004] It is also known in the prior art to ensure redundant valve functions for safety reasons by interconnecting several individual components. Seat valve solutions are particularly suitable for high pressures and flow rates. Due to their large number of components and interfaces, such interconnected solutions are relatively complex in terms of costs and time for installation, commissioning and parameterization, maintenance during operation, and the maintenance of often multiple supplier relationships. In addition, these solutions have design disadvantages, such as their relatively large installation space requirements or energy losses due to numerous flow deflections, for example, when interconnected using base plates.In addition, the commonly used seat valves are not free of overlapping functions, which is why a sudden, temporary pressure increase at the relief outlet when a valve switches from de-energizing (= relieving) to energizing (= applying) a line or machine component—i.e., a fluidic short circuit between the pressure fluid supply and the relief—cannot be reliably prevented by purely design measures. Particularly at high pressures, such short circuits lead to significant undesirable noise emissions and energy losses.

[0005] EP 1 645 755 A2 discloses a soft-start device for compressed air systems with multiple redundant venting switching positions. EP 1 645 755 A2 only discloses solutions for interconnecting components, but not for their structural design. Furthermore, no functions or means for preventing a sudden, temporary pressure increase at the venting outlet when switching a valve from venting to venting a line or machine component are disclosed.

[0006] DE 11 2012 004 574 B4 discloses a flow rate control device with an opening / closing valve, with which the flow rate of a pressurized fluid can be switched between a throttled and an unthrottled state, and with two switching valves arranged in series, each of which can be redundantly connected to a separate relief outlet. The flow rate control device disclosed by DE 11 2012 004 574 B4 does not disclose a low-deflection design or an overlap-free function of the switching valves. Furthermore, no functions or means are disclosed for preventing a sudden temporary pressure increase at the relief outlet when switching a valve from de-energizing to energizing a line or machine component. Disclosure of the invention

[0007] The invention is based on the object of providing a safety valve for switching high pressures and flow rates, which avoids the disadvantages of the prior art. In particular, a safety valve is to be provided that prevents unexpected start-up and ensures safe de-energization. At the same time, a sudden, temporary pressure increase at the relief outlet when switching from de-energization to energization is reliably prevented by purely structural means. Furthermore, the structural design of the safety valve should enable flow guidance with minimal deflection.

[0008] The object is achieved according to the invention by a safety valve according to claim 1. Advantageous developments of the invention are specified in the subclaims.

[0009] The core of the invention is a safety valve for switching high pressures and flows, with a fluid inlet and a fluid outlet, with a first main stage, which in a rest position connects the fluid outlet to a first relief outlet and in a switching position connects the fluid inlet to a fluid connection to a second main stage, the second main stage, which in a rest position connects the fluid outlet to a second relief outlet and in a switching position connects the fluid connection to the fluid outlet, wherein the two main stages are each designed as a seat valve with a linearly movable plunger, and wherein the first main stage has a multi-part plunger, and during the transition from the rest to the switching position, a first plunger part, which can be actuated against a first spring load, initially abuts a second plunger part in a first movement section in a sealing manner,whereby a relief passage to the first relief outlet is closed, and with the movement of the second plunger part in a second movement section or of a further plunger part in a further movement section, a pressure passage between the fluid inlet and the fluid connection to the second main stage is released against a second spring load, and the second main stage has a multi-part plunger, and during the transition from the rest to the switching position, a first plunger part, which can be actuated against a first spring load, initially abuts a second plunger part in a first movement section in a sealing manner, whereby a relief passage to the second relief outlet is closed,and with the movement of the second plunger part in a second movement section or of a further plunger part in a further movement section, a pressure passage between the fluid connection and the fluid outlet is released against a second spring load.

[0010] The seat valve according to the invention is suitable for switching high pressures and flow rates due to the design of the two main stages in seat valve construction. At the same time, its two-channel design always ensures redundant energy disconnection and connection of connected consumers or machine components. Both main stages must always switch before the fluid outlet is pressurized. If only one main stage switches, the fluid outlet remains relieved via the relief outlet of the other main stage. This prevents an unexpected start-up of a connected consumer in the event of an individual fault. Even if one of the two main stages does not switch back to its closed rest position, for example due to a broken spring, the fluid outlet is already relieved via the main stage that switched back.Furthermore, due to the multi-part design of the tappets of the two main stages, a sudden, temporary pressure increase at the relief outlets when switching from de-energizing to energizing is reliably prevented by purely structural means. This is because the first tappet parts actuated first always close the flow paths to the relief outlets before opening the pressurizing passages. The two main stages switch without overlap.

[0011] A reduction in the required installation space for the safety valve is achieved by designing the second tappet part of one or both main stages with an internal fluid channel that opens into a first opening facing the first tappet part. The first opening is closed by the end of the first tappet part facing it when the first tappet part sealingly abuts the second tappet part. This design allows part of the fluid flow guidance during the relief of the fluid outlet to be achieved in a space-saving manner via fluid channels integrated into the second tappet parts.

[0012] A further reduction in installation space is achieved in that the fluid channel, at its end opposite the first opening, opens into a second opening arranged in the side surface of the second tappet part, and the first and second openings open into regions of the safety valve that can be fluidically separated from one another by closing the fluid channel. In an alternative embodiment, the fluid channel, at its end opposite the first opening, is crossed by one or more transverse bores, each of which forms two bore openings in the side surface of the second tappet part, wherein the first opening and the bore openings open into regions of the safety valve that can be fluidically separated from one another by closing the fluid channel.In this design, due to the presence of several outlets of the fluid channel in the side surface, there is a larger tolerance for the installation position of the tappet with regard to any rotational play, so that one bore opening always points in the direction of flow with as little deflection as possible.

[0013] To ensure a controlled pressure increase at the fluid outlet and prevent sudden pressure surges on connected consumers or machine components, a start-up valve is arranged in the flow path between the fluid inlet and the first main stage. This valve can be switched by the pressure applied to the fluid outlet. Once a definable pressure level is reached at the fluid outlet, the start-up valve switches from a smaller flow cross-section to a larger flow cross-section, actuated by this pressure as a switching pressure. The required pressure level is defined by the structural design. In addition, the pressure level can be adjustable, for example, using a spring with adjustable preload.A consumer connected to the fluid outlet or connected machine components are gradually supplied with the full fluidic system power after an initially slow pressure build-up once the start-up valve has switched. The start-up valve can be designed in such a way that it switches completely from a flow path with a smaller flow cross-section to another flow path with a larger flow cross-section, or it can increase the flow cross-section by releasing an additional, wider flow cross-section through the switching process.

[0014] In a compact version of the safety valve with a start-up valve, the smaller flow cross-section is formed by a fluid channel penetrating the shut-off body of the start-up valve. This eliminates the need to design the smaller flow path, for example, as a separate throttle or bypass channel. The throttle channel is integrated into the shut-off body of the start-up valve, for example, a tappet. To adjust the fluidic system performance in the soft-start position, the start-up valve is equipped with an adjustable throttle to change the smaller flow cross-section.

[0015] In a deflection-free design of the safety valve, the pressurizing passages of the first and second main stages or the pressurizing passages of the first and second main stages and the larger flow cross-section of the start-up valve are arranged relative to one another in such a way that, in the switching positions of the valves, a linear flow path is formed between the pressurizing passages or the pressurizing passages and the flow cross-section. This ensures deflection-free and therefore low-loss flow guidance in the switching state of the safety valve when the fluid outlet is pressurized. A further improvement is achieved in that the fluid inlet and the fluid outlet are also arranged in such a way that, together with the pressurizing passages or the pressurizing passages and the flow cross-section, a linear flow path is formed between the fluid inlet and the fluid outlet.

[0016] The first and second main stages are preferably designed to be fluidically actuated, in that the first plunger part is each formed with a piston at its end facing away from the second plunger part, which piston can be subjected to fluid pressure on its side facing away from the first plunger part. In this embodiment, a reduction in the number of external interfaces is achieved by the pressure applied to the pistons via an internal control fluid supply with the pressure present at the fluid inlet, for example, by means of electrically switchable pilot valves.

[0017] To ensure the most compact and integrated design of the safety valve and to reduce the number of components and interfaces required for installation and commissioning, all components of the safety valve are designed as a unit in a common housing.

[0018] Further advantages of the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 a schematic sectional view of a safety valve in the rest position. Fig. 2 a schematic sectional view of the safety valve according to Fig. 1 in a soft start position. Fig. 3 a schematic sectional view of the safety valve according to Fig. 1 in fully engaged operating position. Fig. 4 the sectional view according to Fig. 3 with the flow path marked.

[0019] The Fig. 1 to 4 show a schematic sectional view of the safety valve 1, which is suitable for switching high pressures and flows between a fluid inlet 2 and a fluid outlet 3. The representations of the Fig. 1 to 4are simplified schematic representations of the safety valve 1 without detailed edge areas along the flow guide, which are designed in practice, for example, with smooth surfaces and flow-adapted edge transitions and contours of the fluid passage or valve seat areas, in order to reduce internal friction in a structural design. Fig. 1 shows the safety valve 1 in its de-energized rest position. The fluid outlet 3 serves for connection to a consumer (not shown), which can be, for example, a blow molding tool for blow molding containers from PET preforms. The safety valve 1 has a first main stage 4, which Fig. 1is shown in its rest position, in which it connects the fluid outlet 3 with the first vent outlet 5. The first main stage 4 is designed as a seat valve and has a linearly movable, two-part tappet, which is formed by the lower first tappet part 6 and the upper second tappet part 7. In its rest position, the first main stage 4 connects the fluid outlet 3 with the first relief outlet 5, in that the second tappet part 7 is formed with an internal fluid channel 8, via which a working fluid can escape through an opening gap between the first tappet part 6 and the second tappet part 7 to the first relief outlet 5, wherein the first tappet part 6 is held in its initial position by the spring 9. The safety valve 1 further has a second main stage 10, which in Fig. 1is also shown in its rest position, in which it connects the fluid outlet 3 with the second relief outlet 11. The second main stage 10 is also designed as a seat valve and has a linearly movable, two-part tappet, which is formed by the lower first tappet part 12 and the upper second tappet part 13. In its rest position, the second main stage 10 redundantly connects the fluid outlet 3, in addition to the first relief outlet 5, with the second tappet part 13 being formed with an internal fluid channel 14, via which a working fluid can escape through an opening gap between the first tappet part 12 and the second tappet part 13 via the fluid channel 14 to the second relief outlet 11. The safety valve 1 further has two electrically switchable pilot valves 15 and 16, with which the tappets of the two main stages 4 and 10 can be actuated.The pilot valves 15 and 16 are shown in the illustration. Fig.1 shown schematically with circuit symbols.

[0020] Fig. 2shows the safety valve in a soft start position in which only the two main stages 4 and 10 are switched and which causes a consumer connected to the fluid outlet 3 (not shown) to start up slowly. When the pilot valve 15 is switched, the piston 17 of the first tappet part 6 of the first main stage 4 is internally pressurized via the piston chamber 18 with the valve inlet pressure P1 present at the fluid inlet 2. As a result, the first tappet part 6 is initially moved upwards against the force of the spring 9 in a first movement section until it abuts the second tappet part 7 in a sealing manner, whereby it seals off the fluid channel 8 from the first relief outlet 5.In a further movement, the first tappet part 6 then lifts the second tappet part 7 in a second movement section against the force of the spring 19, whereby the sealing body 20 formed in the upper section of the second tappet part 7 lifts off the valve seat 21 and opens a pressure passage 22 between the fluid inlet 2 and the fluid connection passage 23 to the second main stage 10. After the completion of the second movement section, the first main stage 4 is fully in its switching position, in which a fluid connection is established between the fluid inlet 2 and the fluid connection passage 23 to the second main stage 10. When the pilot valve 16 is switched, the piston 24 of the first tappet part 12 of the second main stage 10 is also internally pressurized via the piston chamber 25 with the valve inlet pressure P1 present at the fluid inlet 2.As a result, the first tappet part 12 is initially moved upwards against the force of the spring 26 in a first movement section until it abuts the second tappet part 13 in a sealing manner, thereby sealing off the fluid channel 14 from the second relief outlet 11. In the further movement, the first tappet part 12 lifts the second tappet part 13 in a second movement section against the force of the spring 27, whereby the sealing body 28 formed in the upper section of the second tappet part 13 lifts off the valve seat 29 and releases a pressurizing passage 30 between the fluid connection passage 23 and the fluid outlet 3. After the completion of the second movement section, the second main stage 10 is fully in its switching position, in which the fluid passage 23 is connected to the fluid outlet 3.Fluid outlet 3 is now supplied with a reduced flow rate compared to the possible system capacity, resulting in a slower pressure buildup at fluid outlet 3, since the start-up valve 31, located in the working fluid flow path between fluid inlet 2 and the first main stage 4, is in its rest position. In this soft-start position, the working fluid flows into the safety valve 1 only via the smaller flow cross-section of the throttle channel 32 in the one-piece tappet 33 of the start-up valve 31. The flow cross-section can be adjusted via the position of the throttle screw 34. If both main stages 4 and 10 are in their switching position, fluid outlet 3 and a connected consumer are supplied with a reduced flow rate, resulting in a slower pressure buildup at fluid outlet 3, ensuring a "soft" or slower start-up of a connected consumer.

[0021] Due to the dual-channel design of safety valve 1, redundant energy disconnection and connection of connected consumers or connected machine components is always guaranteed, even in the event of a fault or failure of one of the two main stages 4 or 10. Both main stages 4 and 10 must always switch before fluid outlet 3 is pressurized. If one of the two main stages 4 or 10 switches due to a fault when the system is unloaded and in the intended rest position, fluid outlet 3 remains unloaded via the relief outlet of the main stage that has remained in its intended unloaded rest position, thus preventing unintentional start-up.If, with the system under pressure and an intended change to the rest position, only one of the two main stages 4 or 10 switches back to its unloaded rest position - for example, in the event of a spring break in the other main stage - fluid outlet 3 is already unloaded via the one of the two main stages 4 or 10 that switched back, thus ensuring redundant energy de-energization. Supplementary sensory condition monitoring can detect such individual errors and achieve higher categories and performance levels in accordance with the standard, as described in the state of the art.

[0022] Due to the two-part design of the tappets of the two main stages 4 and 10, the safety valve 1 also has an overlap-free valve function. A sudden, temporary pressure increase at one of the relief outlets 5 or 11 when switching the main stages 4 and 10 from the relieved rest position to the pressurized switching position is reliably prevented by purely structural means, because the first tappet parts 6 and 12 always first close the flow paths to the relief outlets 5 and 11 before the pressurization passages are opened by the movement of the second tappet parts 8 and 13.

[0023] Fig. 3shows the safety valve in its fully switched operating position, in which, in addition to the two main stages 4 and 10, the start-up valve 31 is also switched, ensuring that the fluid outlet 3 is supplied with the full system power at the maximum flow cross-section. If both main stages 4 and 10 are in their switched position, the fluid outlet 3 and any connected consumer are initially supplied with a reduced volume flow, ensuring a "soft" or slow start-up of a connected consumer. The valve outlet pressure P2 gradually increases. The start-up valve 31 is designed such that it automatically switches from its closed rest position to its open position once the switching pressure at the fluid outlet 3 is reached.In this case, the piston 35 is subjected to the switching pressure present at the fluid outlet 3 via the piston chamber 36, causing the one-piece tappet 33 to move upwards against the force of the spring 37, whereby the sealing body 38 formed in the upper section of the tappet 33 lifts off the valve seat 39 and opens the pressurization passage 40 between the fluid inlet 2 and the first main stage 4. The pressurization passage 40 has a larger flow cross-section than the flow cross-section of the throttle channel 32. In this open switching position of the start-up valve 31, the working fluid flows from the valve inlet 2 into the safety valve 1 via the larger flow cross-section of the pressurization passage 40, causing the valve outlet pressure P2 to rise to the operating pressure and the full fluidic power to be available.

[0024] Fig. 4 shows the schematic sectional view according to Fig. 3with the flow path A shown. Most of the reference numbers were Fig. 4 omitted for illustration purposes in order to better identify the flow path A through the switched and fully opened safety valve 1. The safety valve 1 is designed to be free of deflections, in that all the pressure passages 40, 22 and 30 together with the fluid inlet 2 and fluid outlet 3 are arranged offset from one another in such a way that they form a linear flow path A in the switched position of the start-up valve 31 and the two main stages 4 and 10, as shown in Fig. 4 is marked.

[0025] The safety valve 1 also forms a highly compact and integrated structural unit, which is achieved in particular by the fact that the second tappet parts 7 and 13 and the one-piece tappet 33 are each partially designed as a hollow tappet with the internal fluid channels 8 and 14 as well as the throttle channel 32 and all components are integrated as a structural unit in a common housing.

[0026] To ensure pressure equalization, chambers 41, 42, and 43 are connected to the atmosphere via the vent holes 44, 45, and 46. These vent holes can alternatively be designed as internal channels in the housing, which are vented to the atmosphere individually or collectively. Furthermore, instead of via vent holes or fluid channels, pressure equalization from chamber 42 can also occur via an annular gap between the tappet 6 and the inner housing wall to the first relief outlet 5, i.e., into the next chamber with the same pressure level, as is structurally the case with chamber 47. There, pressure equalization is also achieved via the annular gap 48 between the upper section of the second tappet part 7 and the surrounding housing section, albeit at high pressure level P1 instead of atmospheric level. The same applies to chamber 49, which for this purpose is connected via the vent channel 50 to chamber 47 or another chamber where the pressure level P1 is also present.The piston chambers 18 and 25 can be pressurized and relieved via the connecting channels 51, 52 to the pilot valves 15 and 16, whereby the relief takes place via the pilot valve outlets 53, 54, for example via individual or combined channels through the housing into the atmosphere. List of reference symbols

[0027] 1 Safety valve 2 Fluid inlet 3 Fluid outlet 4 First main stage 5 First relief outlet 6, 12 First plunger part 7, 13 Second plunger part 8, 14 Fluid channel 9, 19, 26, 27, 37 Spring 10 Second main stage 11 Second relief outlet 15, 16 Pilot valve 17, 24, 35 Piston 18, 25, 36 Piston chamber 20, 28, 38 Sealing body 21, 29, 39 Valve seat 22, 30, 40 Pressure passage 23 Fluid connection passage 31 Start-up valve 32 Throttle channel 33 One-piece plunger 34 Throttle screw 41, 42, 43, 47, 49 Chamber 44, 45, 46 Breathing hole 48 Annular gap 50 Breathing channel 51, 52 Connecting channel 53, 54 Pilot valve outlet

Claims

1. Safety valve (1) for switching high pressures and flow rates, comprising a fluid inlet (2), a fluid outlet (3), and a first main stage (4) which, in a rest position, connects the fluid outlet (3) to a first relief outlet (5) and, in a switching position, connects the fluid inlet (2) to a fluid connection of a second main stage (10), and comprising the second main stage (10) which, in a rest position, connects the fluid outlet (3) to a second relief outlet (11) and, in a switching position, connects the fluid connection to the fluid outlet (3), wherein the two main stages (4, 10) are each designed as a seat valve having a linearly movable tappet, characterized in that the first main stage (4) has a multi-part tappet, and during the transition from the rest position to the switching position, a first tappet part (6), which can be actuated counter to a first spring load, initially sealingly abuts a second tappet part (7) in a first movement portion, as a result of which a relief passage to the first relief outlet (5) is closed, and with the movement of the second tappet part (7) in a second movement portion or of an additional tappet part in an additional movement portion, a pressurization passage between the fluid inlet (2) and the fluid connection of the second main stage (10) is opened counter to a second spring load, and the second main stage (10) has a multi-part tappet, and during the transition from the rest position to the switching position, a first tappet part (12), which can be actuated counter to a first spring load, initially sealingly abuts a second tappet part (13) in a first movement portion, as a result of which a relief passage to the second relief outlet (11) is closed, and with the movement of the second tappet part (13) in a second movement portion or of an additional tappet part in an additional movement portion, a pressurization passage between the fluid connection and the fluid outlet (3) is opened counter to a second spring load.

2. Safety valve (1) according to claim 1, characterized in that the second tappet part (7) of the first main stage or the second tappet part (7, 13) of the first and the second main stage is or are formed having an internal fluid channel (8, 14) which opens into a first opening facing the first tappet part (6, 12), wherein the first opening is closed by the end of the first tappet part (6, 12) facing said opening when the first tappet part (6, 12) sealingly abuts the second tappet part (7, 13).

3. Safety valve (1) according to claim 2, characterized in that the fluid channel (8, 14), at its end opposite the first opening, opens into a second opening which is arranged in the lateral surface of the second tappet part (7, 13), and the first and the second opening open into regions of the safety valve (1) which can be fluidically separated from one another by closing the fluid channel (8, 14).

4. Safety valve (1) according to claim 2, characterized in that the fluid channel (8, 14), at its end opposite the first opening, is crossed by a transverse bore or a plurality of transverse bores which each form two bore openings in the lateral surface of the second tappet part (7, 13), wherein the first opening and the bore openings open into regions of the safety valve (1) which can be fluidically separated from one another by closing the fluid channel (8, 14).

5. Safety valve (1) according to any of claims 1 to 4, characterized in that a start-up valve (31) which can be switched by the pressure applied at the fluid outlet (3) is arranged in the flow path between the fluid inlet (2) and the first main stage (4), wherein, when a definable pressure level is reached at the fluid outlet (3), the start-up valve (31) switches from a smaller flow cross section to a larger flow cross section, actuated by said pressure level as a switching pressure,6. Safety valve (1) according to claim 5, characterized in that the smaller flow cross section is formed by a fluid channel penetrating the shut-off body of the start-up valve (31).

7. Safety valve (1) according to claim 6, characterized in that the start-up valve (31) is formed having an adjustable throttle for adjusting the smaller flow path.

8. Safety valve (1) according to any of claims 1 to 7, characterized in that the pressurization passages of the first and the second main stage (10), or the pressurization passages of the first and the second main stage (4, 10) and the larger flow cross section of the start-up valve (31) are arranged relative to one another such that, in the switching positions of the valves, a linear flow path is formed between the pressurization passages, or between the pressurization passages and the larger flow cross section.

9. Safety valve (1) according to claim 8, characterized in that the fluid inlet (2) and the fluid outlet (3) are also arranged such that, together with the pressurization passages, or together with the pressurization passages and the larger flow cross section, a linear flow path is formed between the fluid inlet (2) and the fluid outlet (3).

10. Safety valve (1) according to any of claims 1 to 9, characterized in that the first and the second main stage (4, 10) are designed to be fluidically actuatable, in that the first tappet part (6, 12) is in each case formed having a piston (17, 24) at its end facing away from the second tappet part (7, 13), which piston can be pressurized by fluid pressure on its side facing away from the first tappet part (6, 12).

11. Safety valve (1) according to claim 10, characterized in that the pressurization of the pistons (17, 24) is controlled in each case via a switchable pilot valve (15, 16), wherein the pressurization of the pistons (17, 24) is carried out in each case via an internal control fluid supply, using the pressure applied at the fluid inlet (2).

12. Safety valve (1) according to any of claims 1 to 11, characterized in that all of the components are designed as a structural unit in a common housing.