Pneumatic system

Abstract

A pneumatic system has first and second electrically operated air dryers, each couplable to a compressor through a selection valve. Each electrically operated air dryer can be operated in (i) a loading mode in which the compressor is driven in a drive mode and compressed air is driven through the dryer to one or more consumers and (ii) a non-loading mode in which the EOD inlet connected to the atmosphere by the discharge valve. A pneumatic logic control arrangement is provided for placing the compressor into an energy saving idle mode only when both the first and second electrically operated air dryers are operated in a non-loading mode.

Description

PNEUMATIC SYSTEMFIELD

[0001] Embodiments of the present disclosure relate generally to pneumatic supply systems, especially for industrial or utility vehicles, such as tractors, other agricultural vehicles, construction vehicles and others.BACKGROUND

[0002] Vehicle air supply systems require air dryers to discharge humidity from the air before supplying it to consumers (i.e., system hardware such as pneumatic actuators, pneumatic cylinders and pneumatic motors together with associated actuating valves and reservoirs / accumulators for storing a pressurized air supply for such equipment) on a vehicle. Damp air can cause corrosion in pipes and other components on the vehicle, so before supplying air to consumers (for example, for the vehicle's brake system) the air is usually guided through a dryer. When the air is passing through the dryer to dry the air, this mode of operation is known as a drying or loading mode.

[0003] Due to the restricted load capacity of dryers, a second operation mode, known as a regeneration mode, is required which involves passing air through the reservoir in an opposite direction and discharging it to the atmosphere to remove water deposited in, or on, the drying material of the dryer.

[0004] It is known to use double chamber dryers which comprise two separate dryer reservoirs, so that whilst one chamber is operative in drying the air from the compressor in a loading mode, the other chamber can be operative in a regeneration mode. The shift between the two modes of each drying chamber is time-controlled, so that the dryer may continually be used to dry air.

[0005] Furthermore, Electrically Operated Air Dryers (EODs) are also known. These dryers only require one dryer portion and the shift between the two modes of operation, that isthe switch between the regeneration mode and the loading mode, is controlled electronically. This may be time-controlled by a control unit. For example, the two modes can be controlled by measuring the volume of air passing through the dryer by measuring the compressor time or measuring the pressure rise in the reservoirs (and knowing that a certain pressure rise requires a predetermined air volume). A percentage of the volume of air in the air supply system can be guided back for the regeneration.

[0006] Known pneumatic supply systems also have a compressor idle mode, used when the compressor is not required to supply compressed air through the dryer. The idle mode conserves energy and hence reduces power consumption. The idle mode is used when the air pressure in the system is within the desired range. Moisture sensing may also be used.

[0007] It is known to use two EODs arranged in parallel in a pneumatic supply system so that the EODs can be used alternately, with one operating in a loading mode and the other in a regenerating or idle mode. However, this adds complication to control of the overall system, for example in ensuring the compressor is only switched to an idle mode when neither EOD is operating in a loading mode.BRIEF SUMMARY

[0008] The scope of this disclosure is defined by the claims.

[0009] According to examples in accordance with this disclosure, there is provided a pneumatic system, comprising: a compressor; a selection valve; a first electrically operated air dryer (EOD) and a second EOD, each EOD having an input fluidly couplable to the compressor through the selection valve, an output, configured to be fluidly connected to at least one consumer, and a discharge valve for selectively coupling the EOD input to atmosphere, wherein the selection valve is configured to fluidly connect the input of either the first EOD or the second EOD to the compressor,wherein the outputs of the two EODs are fluidly connected together and to the at least one consumer, wherein each EOD is operable in (i) a loading mode in which compressed air from the compressor is driven through the EOD in a first direction to the at least one consumer and (ii) at least one non-loading mode in which the input to the EOD is fluidly connected to atmosphere by the discharge valve, wherein the compressor has an idle mode which is triggered by a pressure to an idle mode control port, and wherein the pneumatic system comprises a pneumatic logic circuit having an output connected to the idle mode control port and configured for placing the compressor into the idle mode only when both the first EOD and the second EOD are operating in a nonloading mode.

[0010] This system has two air dryers, supplied with compressed air one at a time.This, for example, enables one air dryer to be regenerated while the other is operating in a loading mode. The idle mode of the compressor can be used when both air dryers are in a nonloading mode. To switch the compressor to the idle mode, pneumatic logic control is employed. This simplifies the control system, avoids the need for an additional electrical control signal for compressor mode control and is less prone to error and so meets higher safety standards.

[0011] In embodiments, each EOD comprises: a dryer unit; a one-way output valve configured to allow air to pass only in the first direction from the dryer unit to the EOD output; a regeneration valve connected in parallel to the one-way output valve between the dryer unit output and the EOD output and selectively operable for by-passing the oneway output valve to allow air to flow in a second direction opposite to the first direction from the EOD output through the dryer unit; and a governor valve having an output port fluidly connected to a control pilot port of the discharge valve, the governor valve being selectively operable in an EOD inlet ventingconfiguration to fluidly connect the output port to the EOD output to actuate the discharge valve to fluidly connect the EOD input to atmosphere.

[0012] The pneumatic control valve may comprise a logic AND valve having two control input ports, the pneumatic control valve configured for generating an output fluid pressure at an output port when the fluid pressures at the input control ports are both logic high, wherein the output fluid pressure is used to actuate the idle mode of the compressor.

[0013] In embodiments, the output port of each governor valve is fluidly connected to a respective one of the control ports of the pneumatic control valve, the arrangement being such that a fluid pressure is applied at the respective input control port when the corresponding governor valve is operative in the EOD inlet venting configuration to actuate its respective discharge valve to fluidly connect the respective EOD input to atmosphere.

[0014] The selection valve may be a pneumatically controlled valve, and the output port of the governor valve of one of the first and second EODs may be fluidly connected to a pilot port of the selection valve to control switching of the selection valve. In which case, the selection valve may be biased to fluidly connect the inlet of said one of the first and second EODs to the compressor.

[0015] This disclosure also provides a vehicle comprising the pneumatic system as set out above. The at least one consumer may comprise at least one selected from the following list: rear service brake; front service brake; park brake; trailer brake. tire pressure control system; cab air supply; dust discharge system.

[0016] The vehicle may be an agricultural vehicle, or a combination of a towing agricultural vehicle and a towed implement.

[0017] These are all types of equipment using pneumatic power for different purposes. The vehicle may comprise a vehicle, or a combination of a towing vehicle and a towed implement.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0019] FIG. 1 shows a tractor, as one example of a vehicle that can make use of the pneumatic system of this disclosure;

[0020] FIG. 2 shows a circuit diagram of part of a pneumatic supply system suitable for use in the vehicle of FIG. 1, the pneumatic system having a single EOD;

[0021] FIG. 3 shows the EOD of FIG. 2 operating in a loading mode;

[0022] FIG. 4 shows the EOD of FIG. 2 operating in an idle mode;

[0023] FIG. 5 shows the EOD of FIG. 2 in an overpressure protection mode;

[0024] FIG. 6 shows the EOD of FIG. 2 operating in a regeneration mode;

[0025] FIG. 7 illustrates a first example of a pneumatic supply system of this disclosure; and

[0026] FIG. 8 illustrates a second example of a pneumatic supply system of this disclosure.DETAILED DESCRIPTION

[0027] The subject matter of this disclosure will be described with reference to the Figures.

[0028] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merelyschematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0029] This disclosure provides a pneumatic system for a vehicle having a first EOD and a second EOD, each couplable to a compressor through a selection valve. Each EOD can be operated in (i) a loading mode in which the compressor is driven in a drive mode and compressed air is driven through the EOD to at least one consumer and (ii) at least one nonloading mode in which the EOD inlet is fluidly connected to atmosphere by a discharge valve. A pneumatic logic control arrangement is provided for placing the compressor into an energy saving idle mode when both the first and second EODs are operating in a non-charging mode. The at least one non-loading mode may include a regeneration mode and a holding mode.

[0030] Before describing the concept of this disclosure, examples of the type of vehicle in which the pneumatic system may be used will be discussed, and the known operation of an EOD will be explained.

[0031] The pneumatic system of this disclosure may be applied to a vehicle alone (having pneumatically powered on-board consumers such as pneumatic actuators, pneumatic cylinders and pneumatic motors together with associated actuating valves and reservoirs / accumulators for storing a pressurized air supply for such equipment) or to a vehicle towing or carrying an associated implement. In the latter case, part of the pneumatic system may be in the main vehicle and part of the pneumatic system may be in the associated implement.

[0032] FIG. 1 shows an agricultural tractor 1, as one example of a vehicle that can make use of the pneumatic supply system of this disclosure. The tractor 1 is shown towing an agricultural implement in the form of a planter 2, as one example of an associated implement towed or otherwise carried by a vehicle. The tractor is coupled to the planter by a hitch 3. The planter comprises a seed tank 4 and a control system 5 which regulates delivery of seed to a number of row units 7 mounted to a tool bar 6.

[0033] The pneumatic supply system of this disclosure is not limited to use on tractors or other agricultural vehicles or machines (such as combine harvesters, sprayers and the like) but can be adapted for use with any industrial or utility vehicle requiring a pneumatic airsupply, including construction vehicles, trucks and lorries and others. Indeed, the pneumatic system of this disclosure can also be adapted for use in any pneumatic system using two EODs, whether on a vehicle or not.

[0034] FIG. 2 shows a circuit diagram of a pneumatic supply system 9 having an EOD 100, for example for mounting on a vehicle 1 such as the tractor 1.

[0035] A compressor 10 supplies air to components on the vehicle via the EOD 100. The EOD is connected to various consumers (illustrated schematically at 30, 40, 50, 60) via a consumer branch 20 connected to an output of the EOD. In this example, the consumers 30, 40 are primary consumers and the consumers 50, 60 are secondary consumers. Reservoirs (accumulators) 31, 41 are assigned to the primary consumers 30, 40 and are equipped with pressure sensors 32, 42 to measure the pressure of the compressed air in the consumer branches. Consumers 50 or 60 may also be equipped with respective reservoirs and / or pressure sensors. Generally, the system will try to maintain the reservoirs at a defined pressure level, for example 8.5 bar (850 kPa) to 12.5 bar (1259 kPa), to ensure that they can deliver the required air pressure when required.

[0036] Primary consumers are those whose operation is prioritized over other consumers that are regarded as secondary. Primary consumers may be safety critical. By way of example, in tractors or trucks, primary consumers 30 and 40 may be parallel brake circuits for a dual-circuit service brake. Secondary consumers 50, 60 may be a parking brake, an air suspension of the cab and / or wheels, or the TPCS 61, for example.

[0037] The consumer branch 20 is connected with the various consumers through a multi-circuit protection valve system 21. The multi-circuit protection valve system can take various forms and may be operative to balance the pressure required to be supplied to the primary set of consumers 30, 40 and the secondary consumers 50, 60 and / or to cut the supply to any consumer should a consumer develop a leak. In this way, the integrity of the supply to the remaining consumers is maintained. Furthermore, the multi-circuit protection valve system 21 may be configured to ensure that the supply to the primary consumers is prioritized over the supply to secondary consumers, such as a tire pressure control system, TPCS, 61. Examples of suitable multi-circuit protection valve systems are disclosed in GB1387892 to Robert BoschGmbH and GB1563144A to WABCO Westinghouse GmbH. Other suitable multi-circuit protection valve systems will be known to those skilled in the art.

[0038] Compressor 10 is equipped with idler means 11 to provide an idle mode in which the air flow is reduced to a rate of, for example, 15% of the maximum air delivery, which in a non-limiting example may be in the region of 400 to 1000 liters per minute. Alternatively, this efficiency idle function may be provided by an OFF / ON clutch cutting mechanical drive of compressor 10. Furthermore, the compressor 10 may be electrically driven and the electric supply may be switched off by idler means 11.

[0039] The electrically operated air dryer (EOD) 100 comprises a dryer unit 101 comprising a cartridge filled with drying granules (desiccant), a discharge valve 102, a regeneration valve 103, a governor valve 104, and a one-way output check valve 105. The system has an electronic control unit 70, which may be a computer or CPU. For clarity reasons, the electric connections of valves 102, 103 and 104 to the control unit 70 are only indicated by the dashed arrows. The control unit is coupled to a display 71. The regeneration valve 103 is connected in parallel to the output check valve 105 between the output of the dryer unit 101 and the consumer branch / output of the EOD 100.

[0040] The granule cartridge extracts water from the air passing through it in a first direction from the compressor to the consumers.

[0041] With reference to Figs. 3 to 6, standard operating modes of the pneumatic system are now explained:

[0042] FIG. 3 shows a loading or drying mode.

[0043] When air is required to be supplied to the consumer branch 20, air from compressor 10 flows to the consumer branch 20 in a first direction through dryer unit 101 and check valve 105 as shown by the dotted path LP. During loading, discharge valve 102 is in its closed position 102a biased by spring 102b, as shown in FIG. 3. The regeneration control valve 103 and governor valve 104 are also in their closed positions 103a and 104a biased by springs 103b and 104b respectively. Air flow in an opposite direction, that is from the consumer branch 20 to compressor 10, is prohibited by check valve 105 and the closed regeneration valve 103.

[0044] FIG. 4 shows a non-loading, idle mode. This will also be referred to as a holding mode.

[0045] If the consumers are provided with sufficient air pressure, the pressure in the reservoirs 31, 42 is at a predetermine value which may be in the range of about 8.5 bar (850 kPa) to 12.5 bar (1259 kPa) in this non-limiting example. This pressure is measured by sensors 32, 42 in reservoirs 31, 41. If this pressure is exceeded because compressor 10 is still working, the control unit 70 switches the governor valve 104 from a first, closed position 104a (biased by spring 104b) to a second, open position 104c by energizing solenoid 104d to guide air along path IP1 from the consumer branch 20 through an output port of the governor valve to the compressor idler 11. The output port of the governor valve 104 is also connected to a pilot port 102d of the discharge valve 102 via path DPI so that when the governor valve is in the open position 104c, the discharge valve 102 is moved to its open position 102c for connection of the EOD inlet, and hence the compressor output, to the atmosphere. Thereby the remaining air flow from the compressor (which may be approximately 15% of the maximum air flow of the compressor) is discharged to the atmosphere with minimum resistance via discharge valve 102 along path IP2. The second, open position 104c of the governor valve will also be referred to as an EOD inlet venting configuration as it is the configuration the valve 104 is in when it actuates the discharge valve 102 to vent the EOD input to atmosphere.

[0046] The compressor idler 11 keeps the compressor 10 in this energy saving mode as long as pressure is applied. For normal operation, the compressor idler 11 must be connected to the atmosphere and this is done through governor valve 104 when in closed position 104a.

[0047] FIG. 5 shows an overpressure protection mode.

[0048] If the pressure in the EOD inlet rises to a level above a permitted operating pressure, discharge valve 102 is opened via path OP1 so that the connection of the EOD inlet and compressor 10 to the atmosphere is opened (indicated by path OP2). This function is a safety function when the electronic control fails, or a blockage occurs which would also result in an incorrect pressure detection at pressure sensors 32,42. In a non-limiting example, the discharge valve 102 may be arranged to fluidly connect the EOD inlet to atmosphere when the pressure in the EOD inlet rises to around 19 bar (1900 kPa).

[0049] FIG. 6 shows a non-loading, regeneration mode.

[0050] The granules in the cartridge of dryer unit 101 can be regenerated by passing a purgative air flow through the cartridge in the reverse direction. Regeneration through the cartridge of dryer unit 101 may be achieved by using air from consumer reservoirs 31, 41 or any other reservoir connectable in a similar manner. For example, the EOD 100 may be provided with its own regeneration reservoir. Governor valve 104 is opened to position 104c (the EOD inlet venting configuration) first so that the compressor 10 is brought into the idle mode (as explained above for the idle mode) and air flows along path I Pl. In addition, regeneration valve 103 is moved from its closed position 103a (biased by spring 103b) to the open position 103c by energizing solenoid 103d so that air from the consumer branch 20 (or other source of air used for regeneration) can by-pass the check valve 105 and enter the cartridge of dryer unit 101 along path RP1 to pass through the dryer unit in the opposite direction to the first direction. As discharge valve 102 is already opened to position 102c via path IP1, DPI and port 102d, the air regenerating the dryer unit cartridge 101 and any air coming from the compressor 10 in the idle mode is discharged to the atmosphere.

[0051] This disclosure relates to pneumatic systems having two EODs alternately connectable between a compressor and the consumers. This enables one EOD to supply dry air while the other is regenerating or operating in a holding mode. However, when they share a compressor 10, the compressor can only be placed into an energy saving idle mode when a supply of compressed air is not needed by the consumers and both EODs are operating in a non-loading mode. This complicates the control of the compressor.

[0052] This disclosure provides a pneumatic system, a first example 209 of which is shown in FIG. 7. The pneumatic system 209 comprises a compressor 10, a first EOD 200 and a second EOD 210, each having an input 201, 211 which can be alternately fluidly connected to the compressor 10 through a selection valve 220. The selection valve 220 couples the input of either the first EOD or second EOD to the compressor output. The EODs each have an output 208, 218 forming part of a consumer branch 207, 217. The consumer branches 207, 217 and outputs 208, 218 of the two EODs are fluidly connected to each other and connected to the consumers through a multi-circuit protection valve system 21.

[0053] In one example, each EOD has a structure and operation similar to that explained above for a single EOD system with reference to FIGs. 2 to 6.

[0054] Thus, as shown for the first EOD 200, there is a dryer unit 202 comprising a cartridge filled with drying granules, a discharge valve 203, a regeneration valve 204, a governor valve 205 and an output valve (check valve) 206. The discharge valve 203 is for selectively coupling an input 201 to the first EOD 200 to the atmosphere and is thus between an input side of the dryer unit 202 and a vent to the atmosphere.

[0055] The one-way output check valve 206 is located between an output to the dryer unit and a consumer branch 207 leading to an output 208 of the EOD which is fluidly connected to the one or more consumers 230, 234. In addition, the output side of the dryer unit 202 is fluidly connectable to the consumer branch 207 and EOD output 208 through the regeneration valve 204 in parallel to the output check valve 206. The regeneration valve 204 is thus capable of selectively coupling the consumer branch 207 and the EOD output 208 to the output of the dryer unit to allow a flow through the dryer unit in a reverse direction for regeneration. The governor valve 205 has an input port fluidly connected to the consumer branch 207 and the EOD output 208 and an output port 205a fluidly connected to a pilot control port 203a of the discharge valve 203, as indicated by the dashed line DPI.

[0056] The electric connections of valves 204, 205 to the control unit 70 are indicated by dashed lines and may be wired or wireless connections.

[0057] The second EOD 210 is similarly constructed having a dryer unit 212 comprising a cartridge filled with drying granules, a discharge valve 213, a regeneration valve 214, a governor valve 215, and an output valve (check valve) 216. The discharge valve 213 is for selectively coupling an input 211 to the second EOD to the atmosphere and is thus between an input side of the dryer unit 212 and a vent to the atmosphere. A consumer branch 217 of the second EOD leads to an output 218 of the second EOD and is fluidly connected to the consumer branch 207 of the first EOD upstream of the consumer multi-circuit protection valve system 21. The second EOD 210 is constructed and operated in a similar manner to the first EOD 200 as described above, to which the reader should refer.

[0058] In each of the first and second EODs 200, 210, the respective discharge valve 203, 213, regeneration valve 204, 214, governor valve 205, 215, and one-way output check valve 206, 216 correspond to and perform similar functions to the discharge valve 102, regeneration valve 103, governor valve 104, and output check valve 105 in the known single EOD system described above in relation to FIGs. 2 to 6.

[0059] The multi-circuit protection valve system 21 supplies a set of primary consumers 230 via reservoirs 232 and secondary consumers 234. FIG. 7 also shows pressure sensors 244 for providing pressure feedback to the control unit 70.

[0060] As explained above, each EOD 200, 210 can be operated in a loading mode in which the compressor is driven in a drive mode and compressed air is driven through the dryer unit to the one or more consumers and non-loading modes, which include a holding mode and a regeneration mode.

[0061] The compressor 10 has an energy saving idle mode which is used when the system pressures are such that operation of the compressor is not needed. In the idle mode, the compressor 10 is switched to an idle state. The compressor may be turned off in the idle state, but it may remain partially actuated delivering a lower pressure and air flow than when being driven to provide air to the consumers through one of the EODs 200, 210.

[0062] To the extent described above, the implementation of two EODs is known.

[0063] In accordance with this disclosure, the idle mode of the compressor 10 is triggered by a fluid (air) pressure to an idle control port 240. A fluid pressure control line 242 is fluidly connected to the idle control port 240.

[0064] There are many compressor designs with an energy saving idle mode. For example, most two-cylinder compressors use the pressure in an energy saving pipe to open a valve between the two cylinders. Air is no longer compressed, and output is instead only cycled between the two cylinders.

[0065] In one-cylinder compressors, the pressure in an energy saving pipe may be used to open a valve, so that air is no longer compressed but is exhausted to atmosphere.

[0066] Another possibility is a separate valve between a cylinder and the suction port. Pressure in an energy saving pipe opens this valve and air in the cylinder will flow back to suction port.

[0067] For generating the pressure supplied along the pressure control line 242 to the idle control input port 240 of the compressor, a pneumatic logic circuit is used. In the embodiment shown, the pneumatic logic circuit comprises a pneumatic AND logic control valve 250 having an output 252 fluidly connected to the idle control input port 240 by the pressure control line 242. The control valve 250 has two inputs 250a, 250b. The output port 205a, 215a of the governor valve 205, 215 of each of the first and second EODs 200, 210 is fluidly connected to a respective one of the inputs 250a, 250b of the control valve 250. Thus, each input pressure is high when the respective governor valve 205, 215 is opened to actuate its associated discharge valve 203, 213 during a non-loading mode of operation of the respective EOD and is low when the respective EOD is operating in a loading mode and the governor valve 205, 215 is closed.

[0068] The control valve 250 is designed to deliver a pressure which places the compressor into the energy saving idle mode only when both the first and second EODs are operating in a non-loading mode, namely when both inputs are high.

[0069] The idle mode of the compressor is thus used when both air dryers are in a nonloading mode and no compressed air is being provided to the consumers. The use of pneumatic logic control simplifies the control system and avoids the need for an additional electrical control signal for the compressor mode control. The use of pneumatic logic control is also less prone to error and so provides for increased safety levels.

[0070] The control valve 250 functions as a pneumatic AND logic valve. The valve will only produce an output fluid pressure signal at the output 252 for transmission to the compressor idle control port 240 when there is a fluid pressure at both inputs 250a, 250b to the control valve (i.e ., when both governor valves 205, 215 are in the EOD inlet venting configuration). The control valve 250 forwards the lowest of the fluid pressures at the inputs 250a, 250b to the output 252. When both governor valves 205, 215 are in the EOD inlet venting configuration, they will forward the same pressure to the two control valve inlets 250a, 250b asthey are fluidly connected, and this pressure will be forwarded to the output 252 and hence to the compressor idle control port 240. When a governor valve 205, 215 is in its closed position, its output port 205a, 215a is connected to atmosphere so that no fluid pressure is retained in the lines to the respective input 250a, 250b of the control valve 250 or the pilot port 203a, 213a, of the respective discharge valve 203. Since control valve 250 forwards the lowest fluid pressure present at either of the inlets 250a, 250b to the output 252, when at least one of the governor valves 205, 215 is in the closed position so that its output port 205a, 215a is vented to atmosphere, the output 252 of the control valve 250 and the control line 242 to the idle control port 240 will also be vented to atmosphere so that the compressor 10 will not be idled.

[0071] If either of the pressure sensors 244 (which are connected to the same pressure level and multiple sensors are only provided for a verification check) indicates that the main consumer reservoirs 232 have reached their target operating pressure (e.g., about 8.5 bar (850 kPa) to 12.5 bar (1259 kPa) both governor valves 205, 215 are switched to the open, EOD inlet venting configuration resulting in idling of the compressor 10. Since the discharge valve 203, 213 of both EODs will be actuated to fluidly connect the EOD inputs to atmosphere, any reduced output from the compressor will be vented to atmosphere through the discharge valve 203, 213 of whichever EOD 200, 210 is fluidly connected to the compressor by the selection valve 220.

[0072] The pneumatic logic arrangement avoids the compressor being idled by one governor valve alone. The control valve 250, with two fluid pressure inputs 250a, 250b, is used as a purely pneumatic logic solution to idle the compressor only when both governor valves 205, 215 are in the open, EOD inlet venting configuration. This avoids the need for any internal changes to the EODs. Other pneumatic AND logic valve arrangements could be adopted to forward a pressure signal to idle the compressor only when both governor valves 205, 215 are in the open, EOD inlet venting configuration. For example, one alternative logic circuit may comprise two pneumatically piloted 2 / 2 way valves (two ports / two positions) arranged in series between a fluid pressure source and the compressor idle control port 240, with the pilot port of each valve being fluidly connected to the output port 205a, 215a of a respective one of the governor valves 205, 215. When both governor valves are in the EOD inlet ventingconfiguration, the pilot ports of both valves is pressurized so that the two valves open to forward a fluid pressure signal to the idle control port 240.

[0073] The non-loading modes of operation for each EOD 200, 210 include a holding mode in which the governor valve 205, 215 is in the EOD inlet venting configuration but the regeneration valve 204, 214 is closed, and a regeneration mode in which the regeneration valve 204, 214 is also in the open position. When an EOD is being operated in a regeneration mode, air for regeneration may be provided from the consumers and / or from the other EOD if it is being operated in a loading mode. When an EOD 200, 210 is being operated in a holding mode, air pressure is provided at the output port 205a, 215a of the governor valve to open the discharge valve 203, 213, but air is not allowed to flow in the reverse, second direction through the dryer unit 202, 212.

[0074] The compressor 10 can be placed in idle mode when both EODs are being operated in a holding mode, or both are being operated in a regeneration mode, or when one is being operated in a holding mode and the other in a regeneration mode. The two EODs may both be operated in a holding mode when the air pressure in the consumers is sufficiently high that no further air need be provided by the compressor but where neither EOD 200, 210 requires regenerating.

[0075] In the example of FIG. 7, the selection valve 220 is a pneumatically controlled valve. It is a 3 / 2 way valve (three ports / two positions), which is pneumatically pilot controlled.

[0076] A fluid pressure at the supply for consumer 234 is used to control the selection valve 220. The pressure is provided to an electrically actuated valve 260 for selectively routing the consumer pressure to the selection valve 220 pilot port 220a or blocking the control port of the valve 260 (in the position of the valve 260 shown in FIG. 7). The switching of the valve 220 is thus controlled by switching valve 260 using electronic control unit 70. It should be appreciated that the air pressure forwarded to the selection valve 220 by the electronically actuated valve 260 need not be taken from the consumer 234 but can be taken from any suitable location in the pneumatic circuit.

[0077] In the example of FIG. 8, the pneumatic system 209' is substantially identical to the system 209 of the example shown in FIG. 7 and as described above, except for thearrangement for piloting the selection valve 220, which will now be described. In the pneumatic system 209', the selection valve 220 is again a pneumatically controlled valve, but the pilot control port 220a is fluidly connected to the output port 205a, 215a of the governor valve 205, 215 of one of the EODs 200, 210. In the embodiment shown, the pilot port 220a of the selection valve 220 is fluidly connected to the output port 215a of the governor valve 215 of the second EOD 210 by line 262. The selection valve 220 is biased by a spring to fluidly connect the output of the compressor 10 to the second EOD 210 in a default setting as shown in FIG. 8. When the second EOD 210 is operated in a non-loading mode, say because it requires regeneration, the governor valve 215 of the second EOD 210 is moved to the open, EOD inlet venting configuration, which, in addition to actuating the discharge valve 213 and sending a pressure signal to one of the inputs 250b of the control valve 250, will forward a pressure to the pilot port 220a of the selection valve 220 moving the valve against the spring bias so that the first EOD 200 is fluidly connected to the compressor output. The first EOD 200 can then be operated in a loading mode to dry air forwarded from the compressor 10 to the consumers. The second EOD can be operated in a holding mode or a regeneration mode by also opening the regeneration valve 214.

[0078] If the second EOD 210 is subsequently to be operated in a loading mode, say when regeneration of the first EOD 200 is required, the governor valve 215 of the second EOD 210 is moved to the closed position (equivalent to position 104a in the prior art arrangements described above in relation to FIGs. 2 to 6) so that its output port 215a and the fluid line 262 to the selection valve pilot port 220a is vented to atmosphere. The selection valve 220 will then be biased by its spring to the default position so that the second EOD 210 is again connected to the output of the compressor. When both EODs 200, 210 are operated in a non-loading mode, the pressure signal from the governor valve 215 of the second EOD 210 will hold the selection valve 220 so that the first EOD 200 is fluidly connected to the compressor 10 and any output from the compressor will be vented to atmosphere through the discharge valve 203 of the first EOD.

[0079] It will be appreciated that the above arrangement could be reversed, with the output port 295a of the governor valve 205 of the first EOD 200 fluidly connected to the pilotport 220a of the selection valve 220 and the selection valve biased by its spring to fluidly connect the first EOD to the compressor output in a default position.

[0080] FIG. 8 illustrates an alternative position for a pressure sensor 244 between the outputs of the EODs and the muti-circuit protection valve 21 (i.e., upstream of the multi-circuit protection valve). This can be used in addition to the pressure sensors 244 associated with the primary consumer circuits downstream of the multi-circuit protection valve or as an alternative for proving an input for controlling the governor valves.

[0081] As explained above, this disclosure may be applied to any vehicle having a pneumatic system for supplying consumers (i.e., on-board or external equipment) with pneumatic power. The vehicle may be an agricultural vehicle, such as a tractor, or other type of commercial vehicle.

[0082] By way of example, the one or more consumers may comprise one or more selected from the following list: rear service brake; front service brake; park brake; trailer brake; tire pressure control system; cab air supply; dust discharge system.

[0083] These are all types of equipment using pneumatic power for different purposes. The vehicle may comprise a vehicle, or a combination of a towing vehicle and a towed implement or an agriculture al machine, especially a self-propelled agricultural machine such as a combine harvester.

[0084] The multi-circuit protection valve system 21 for example may comprise multiple circuits, e.g. four circuits. Different circuits may operate at different pressures and may be associated with their own reservoirs. For example, the rear service brake, front service brake, park / trailer brake may each be supplied by a separate circuit. The fourth circuit may then supply the secondary consumers.

[0085] Rather than applying a pneumatic pressure to a pilot port 240 of the compressor, the compressor could be idled by using the idle pressure signal to acuate a clutch to disengage drive to the compressor or to otherwise switch the compressor off. For example, if the compressor is driven by a hydraulic or electric motor, the idle pressure signal could be used to stop the motor.

[0086] Within the scope of this application, it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.

[0087] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the subject matter of this disclosure, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0088] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0089] Any reference signs in the claims should not be construed as limiting the scope.

[0090] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

Claims

CLAIMS1. A pneumatic system, comprising: a compressor (10); a selection valve (220); a first electrically operated air dryer (EOD) (200) and a second EOD (210), each EOD having an input (201, 211) fluidly connectable to the compressor (10) through the selection valve (220), an output (208, 218), configured to be fluidly connected to at least one consumer, and a discharge valve (203, 213) for selectively fluidly connecting the EOD input (201, 211) to atmosphere, wherein the selection valve (220) is configured to fluidly connect the input (201, 211) of either the first EOD or the second EOD to the compressor, wherein the outputs (208, 218) of the two EODs are fluidly connected together and to the at least one consumer, wherein each EOD (200, 210) is operable in (i) a loading mode in which compressed air from the compressor is driven through the EOD in a first direction to the at least one consumer and (ii) at least one non-loading mode in which the input (201, 211) to the EOD is fluidly connected to atmosphere by the discharge valve (203), wherein the compressor (10) has an idle mode which is triggered by a pressure to an idle control port (240), and wherein the pneumatic system comprises a pneumatic logic circuit (250) having an output (252) fluidly connected to the idle control port (240) and configured for placing the compressor into the idle mode only when both the first EOD and the second EOD (200, 210) are operating in a non-loading mode.

2. The pneumatic system of claim 1, wherein each EOD comprises: a dryer unit (202, 212);a one-way output valve (206, 216) between an output of the dryer unit and the output (208, 218) of the EOD, the one-way output valve configured to allow air to pass only in the first direction from the dryer unit to the EOD output (208, 218); a regeneration valve (204, 214) connected in parallel to the one-way output valve between the dryer unit output and the EOD output and selectively operable for bypassing the one-way output valve (206, 216) to allow air to flow in a second direction opposite to the first direction from the EOD output through the dryer unit; and a governor valve (205, 215) having an output port (205a, 215a) fluidly connected to a control pilot port (203a, 213a) of the discharge valve (203, 213), the governor valve being selectively operable in an EOD inlet venting configuration to fluidly connect the output port to the EOD output (208, 218) so as to actuate the discharge valve to fluidly connect the EOD input (201, 211) to atmosphere.

3. The pneumatic system of claim 2, wherein the pneumatic control valve (250) comprises a logic AND valve having two input control ports (250a, 250b), the pneumatic control valve configured for generating an output pressure at an output port (252) when the pressures at the input control ports are both logic high, wherein the output pressure is used to actuate the idle mode of the compressor.

4. The pneumatic system of claim 3, wherein the output port (205a, 215a) of each governor valve (205, 215) is fluidly connected to a respective one of the control ports (250a, 250b) of the pneumatic control valve (250), the arrangement being such that a fluid pressure is applied at the respective input control port (250a, 250b) when the corresponding governor valve (205, 215) is operative in the EOD inlet venting configuration.

5. The pneumatic system of any one of claims 2 to 4, wherein the selection valve (220) is a pneumatically controlled valve,and the output port (205a, 215a) of the governor valve (205, 215) of one of the first and second EODs is fluidly connected to a pilot port (220a) of the selection valve to control switching of the selection valve.

6. The pneumatic system of claim 5, wherein the selection valve (220) is biased to connect the inlet of said one of the first and second EODs to the compressor.

7. A vehicle comprising: the pneumatic system of any one of claims 1 to 6; and the at least one consumer that is supplied by the pneumatic system.

8. The vehicle of claim 7, wherein the at least one consumer comprises at least one selected from the following list: rear service brake; front service brake; park brake; trailer brake. tire pressure control system; cab air supply; dust discharge system.

9. The vehicle of claim 7 or claim 8 comprising an agricultural vehicle, or a combination of a towing agricultural vehicle and a towed implement.

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