Methods and apparatus for ventilating carriages

Abstract: A ventilation control device (1) for a high-speed train carriage is operable in conjunction with a ventilating blower. A deflectable spring flap (2) is mounted to extend across the ventilation duct in the air flow path. When deflection of the flap (2) reaches a threshold level corresponding to possible passenger discomfort, the flap (2) operates a limit switch (4) positioned behind it. This activates a driving solenoid (5) to close a shutter (7) which shuts off the flow through the duct. A timer holds the shutter closed for a predetermined period, after which it is re-opened. Use of a microprocessor-controlled continuous sensor and damper can thereby be avoided, while cutting out very large pressure fluctuations.

Description: This invention relates to methods and apparatus for ventilating carriages, and in particular embodiments to ventilating the carriages of high-speed trains. Conventionally, train carriages are ventilated by intake and exhaust ducts with respective electric blowers by which air is collected from outside a carriage passed through the interior space of the carriage, and exhausted to the exterior. During operation the exterior air pressure varies substantially. In particular it fluctuates when two trains pass one another, when a train enters or leaves a tunnel, and most particularly when two trains pass one another in a tunnel. The magnitude of the fluctuation varies approximately in proportion to the square of the train velocity, assuming closely-matched sectional areas for the trains and the tunnel. In recent years, faster and faster trains have been developed. Speeds well in excess of 250km/h are routinely achieved by trains on conventional tracks. Trains running faster than 300km/h are being introduced, and speeds of over 400km/h are envisaged for the new generation of linear magnetic drive trains running on special magnetic tracks. In these circumstances there are more serious problems to overcome as regards ventilation, in view of the pressure fluctuations mentioned above. Specifically, the pressure is likely to vary beyond the operating capacity of any reasonable blower used in a ventilation system. That is, the pressure may rise so high that air is forced back in through the ventilation exhaust duct, or falls so low that air is sucked out through the intake duct. In either case a sudden change of pressure occurs inside the car, giving the passengers the well-known and unpleasant "blocked ear" sensation. Blower power has been increased in an effort to meet the problem. As train speed increases, however, these modifications are not sufficient to prevent sudden pressure changes in the carriage. Other measures have been proposed which aim to reduce sudden ventilation air flow changes arising from sudden pressure changes. JP-A-227850/1987 describes a sensor which continuously monitors pressure inside the carriage. A micro-processor connected to the sensor controls the continuous adjustment of throttle valves provided in the intake and exhaust ducts. Our own earlier EP-A-315108 describes an air flow regulator comprising two flexible plates projecting across the duct from fixing points on opposite sides thereof. Bending of the plates caused by increased pressure difference reduces the flow gap between the plates and hence the flow rate. This has the advantage of not requiring any control system. EP-A-315108 also describes a controlled system with a pressure sensor on the outside of the carriage near the air intake. The sensor is connected to a control processor which, when either the rate of pressure change or the degree of pressure change exceeds a predetermined respective limit, controls the movement of an adjustable damper in the duct and/or the power exerted by the blowers in order to avoid passenger discomfort. Prior art systems using continuous pressure monitoring with a sensor and control processor are complicated. Furthermore, they are not satisfactory when extreme pressure variations occur. The system using flexible plates is simple, but substantial clearances are needed for free movement of the plates and so the device gives insufficient air-tightness to deal with large pressure differences. Problems addressed herein include the provision of novel ventilation devices for carriages, carriages with novel ventilation systems, and novel methods of ventilating carriages. Preferably it is sought to provide such devices, carriages and methods which are adaptable to the extreme demands imposed by very high-speed trains. In a first aspect, the invention provides a ventilating device for the interior of a high-speed carriage, comprising a shutter for closing a ventilating duct communicating between the interior and the exterior of the carriage, and characterised by a sensing device having a movable element subject to air flow between the interior and exterior of the carriage, and means actuated by the sensing device only after a predetermined degree of movement of the movable element thereof, to cause the shutter to close the ventilating duct. The sensing device, shutter and shutter closing means may be provided for both the intake duct and the exhaust duct of a carriage. By using as a sensor a movable element which is subject to the actual air flow between the interior and exterior, the sensing device can be designed and adjusted on an empirical basis to obtain satisfactory results. The shutter closing means is not actuated by the sensing device until the predetermined movement has occurred, so the actuation means can be very simple e.g. a mechanical limit switch. This may be actuated by being contacted by the movable element itself as it reaches the predetermined threshold level. The movable element is desirably a flap which extends across the duct. Usually it is moved by the air flow against a restoring force, preferably a spring restoring force. It may itself form a leaf spring, and/or be moved against one or more separate restoring springs. In the preferred form, it is mounted for a swinging movement in the duct i.e. with one fixed end. In a second aspect, the invention provides a ventilating device for a train carriage, comprising a duct and a fan for blowing air through the duct; a shutter movable to close the duct, and means for driving the movable shutter; a movable flap extending across the duct so as to be moved against a restoring force under the influence of air blowing through the duct, in which the movable flap mechanically actuates the shutter-driving means at a predetermined degree of movement of said flap. Such a device may be mounted at an exterior portion of a train carriage e.g. underneath the carriage. In a third aspect the invention provides a train carriage having a ventilator system comprising an intake blower for blowing air from the exterior to the interior of the carriage through an intake duct, and an exhaust blower for blowing air from the interior to the exterior of the carriage through an exhaust duct; characterised in that air flow sensing devices are provided in the intake and exhaust ducts, comprising means for determining when air flow therein reaches a predetermined threshold value, and in that shutters are operatively connected to the sensing devices and operate, so as to close off air flow through the ducts, only when the air flow threshold value is reached. Usually a similar ventilation system would be provided for each carriage of a train comprising plural carriages. Because the ventilating control device described above does not necessarily require any microprocessor monitoring system, the device can be operated using only AC power, because that is generally all that the shutters and sensing devices need. For safety and convenience, it is also desired that means for de-activating the shutter-closing drive in the event of a defect thereof are also connected to cut off the respective blower at the same time. This can avoid damage and make it easier to locate faults. In a fourth aspect the invention provides a method of ventilating a high-speed carriage in which an intake blower blows air from the exterior to the interior of the carriage through an intake duct, and an exhaust blower blows air from the interior to the exterior of the carriage through an exhaust duct, characterised by contacting air flow in the exhaust and intake ducts against respective movable sensing elements; shutting off a respective one of said ducts when the degree of movement of the movable element therein reaches a predetermined value; holding said duct in the shut off condition for a pre-set time period, and then re-opening said duct to allow resumption of air flow. This methodology obviates the continuous sensing which was required in the prior art methods, and thereby obviates the complicated and sensitive apparatus required for that sensing. Even when a prolonged period of pressure imbalance occurs, the air flow is "sampled" by the sensing element as each pre-set time period expires; if the air flow is still too great then the duct is immediately closed again. The method may involve shutting both the intake and exhaust ducts when the rate through either reaches the critical value. Embodiments of the invention are now described by way of example, with reference to the accompanying drawings in which Figure 1 is a schematic side view of a train car indicating a ventilation system; Figure 2 is a broken away perspective view of a first embodiment of a ventilating device; Figure 3 is a section at A-A of Fig. 2 showing, partly schematically, the operation of the device; Figure 4 is a section at B-B of Fig. 2, showing a shutter; Figure 5 is a section at C-C of Fig. 2, showing a leaf spring flap; Figure 6 is a section down the middle of Fig. 4, showing mounting of the shutter; Figure 7 illustrates a relationship between displacement of the leaf-spring flap and the flow rate through the device; Figure 8 shows a relationship between pressure conditions and passenger comfort in a carriage; Figure 9 is a system diagram for the ventilation system of one carriage; Figure 10 shows the variation of pressure and ventilation parameters typical for the lead car of a train passing through a tunnel, and Figure 11 shows a second embodiment of ventilation device in a view corresponding to Fig. 3. A railway carriage 70 has a ventilation system consisting basically of an electric-powered intake blower 50 taking air in from underneath the car and leading into an intake duct 51 which typically extends along the ceiling of the car. See Fig. 1. The duct along the ceiling has a plurality of vents in a generally known manner. Air is exhausted from the interior space of the carriage 70 by a corresponding exhaust duct 53 which extends along the interior space near floor level. An electric powered exhaust blower 52 draws air from the interior space through the exhaust duct 53 and to the exterior, also underneath the carriage. Such a lay-out is generally known. The exterior mouths of the intake and exhaust ducts are each provided with a ventilator control device 1 which is described in more detail with reference to Figures 2 to 6. Each control device is formed in a section of steel duct having a rectangular cross-section, mounted towards the exterior relative to the blower fan. The duct section has an upstream opening 101 and a downstream opening 102. Towards the upstream opening, a metal leaf spring 2 projects about three-quarters of the way across the duct, from a fixed mounting 12 at one side thereof. Leaf spring 2 is a rectangular sheet of springy steel e.g. cold-rolled stainless steel strip made for spring applications. It occupies most of the height of the duct, but only about three-quarters of the width (in its elongate direction). A stopping bar 3 and, by a bracket 4b, a limit switch unit 4 are fixed to the duct wall a short distance downstream of the leaf spring 2. A sufficient bending displacement of the leaf spring 2 (as seen in Fig. 3) causes it to contact a movable actuating element 4a of the limit switch unit so as to close the switch. This degree of movement also brings the leaf spring 2 up against the stopper 3 so that it cannot move further and damage itself or the switch. Further downstream a shutter arrangement 6,7 extends right across the duct. This consists of a fixed shutter wall 7 which occupies the entire duct area but towards one side of the duct has a series of ventilating apertures 17 forming a grille allowing ventilating air through. The other element is a movable shutter plate 6 which is superimposed over the grille area of the fixed plate 7, on the upstream side, and itself has apertures 16 forming a grille corresponding to that of the fixed plate. The two plates therefore co-operate to form a shutter of the "hit or miss" type in which only a small length of movements of the shutter plate 6, corresponding to the pitch of the apertures, is needed to pass between the fully open and fully closed conditions. The apertures are parallel elongate ovals. The shutter plate 6 is mounted between linear bearing runners 11 at the top and bottom of the duct (see Fig. 6) to enable this movement, which is transverse to the general flow direction of the duct. A small laminar gap is left between the two plates 6,7 so that they do not make frictional contact. Where the two sets of apertures 16,17 are unmatched as seen in Fig. 4, scarcely any air can flow past the shutter. With the apertures 16,17 in register a substantial air flow is possible (indicated in Fig. 6). A linear solenoid 5 is fixed relative to the duct by securing it to the fixed plate 7 via a bracket 5b. The moving shaft 5a of the solenoid 5 is fixed to a projecting lug on the shutter plate 6 so that the solenoid 5 when actuated drives the shutter to its closed condition. This comprises a return spring 8 engaging between the opposite side of the duct and another lug on the shutter plate 6, which returns the shutter to the open condition when the solenoid 5 is not activated. Basic operational conditions for the device 1 are shown schematically in Fig. 3 (Fig. 9 is more comprehensive). Medium voltage AC power supplied primarily to the blower motors is diverted through a transformer 9 which brings it down to the specific voltage of the solenoid 5, passing thereto via a control board 10 which links in the limit switch 4 and also has an electromagnetic contactor described later. Briefly, the leaf spring 2 is deflected by air flowing through the ventilation duct, to a degree dependent on the air flow rate and determinable empirically. After a predetermined degree of deflection, as shown in Fig. 3, the rear surface of the leaf spring actuates the limit switch 4 which activates the linear solenoid 5. The movable plate 6 is then immediately driven to close the shutter arrangement. Because only a very short stroke S is required, the operation is very quick. In Fig. 7, the line P shows the characteristic of the leaf spring. Q indicates the rated flow rate for the ventilation system. R represents an excessive flow rate at which the ventilator should be shut off, to prevent pressure changes inside the car causing the "blocked ear" phenomenon. R can be determined from empirical studies, the results of which are represented in Fig. 8. Fig. 8 shows how either a very large pressure change or a very fast pressure change can cause the blocked ear feeling. Region X is a tolerable region; region Y is a region of discomfort while the line between them represents onset of the blocked ear feeling. In this way, from Fig. 7, the leaf spring displacement corresponding to the shut-off air flow value R can be determined, and the limit switch placed accordingly. Of course, it is always possible to fix the limit switch and select the spring characteristic of the leaf spring instead. Fig. 9 is a more detailed electric system diagram for the ventilation control of one carriage. The circuits for controlling the intake blower and the exhaust blower are the same. Electricity is collected from an aerial cable at AC25kV using a pantograph 20 via a vacuum circuit breaker 21. A main transformer 22 reduces the voltage to AC440V and the motors 26,31 for the intake and exhaust blowers are powered from this. The motors are connected by way of circuit breakers 23 (for wiring) and also electromagnetic contactors 24 and thermal relays 25 that serve as excess current protection devices. Capacitors 27 are provided for starting the three-phase motors. Power for the linear solenoid 5 is taken from the output side of the electromagnetic contactor 24. A further thermal relay 29 is provided for the solenoid 5 in order to detect defects therein, and is arranged to cut off the main electromagnetic contactor 24 in the event of such a defect being detected. In this way any such defect results in power being cut off from both the solenoid 5 and also the electric blower concerned, so that the blowers do not operate, problems can be easily detected and damage minimised. Furthermore, since each blower has its own leaf spring 2, limit switch 4 and solenoid 5, any problems with these can be confined to one ventilator control unit only and other control devices in other carriages need not be affected. Fig. 9 also reproduces the limit switch 4 and its relationship with the electromagnetic contactor 28 which actives and inactivates the solenoid 5. The circuit further includes a timer 30 which keeps the solenoid 5 connected to power for a predetermined time even when the limit switch 4 is no longer contacting. The pre-set period T₁ imposed by this timer 30 should normally be at least 5 seconds, more preferably 10 to 25 seconds and most probably 15 to 20 seconds. Operation of the ventilation device 1 is now considered with reference to some operational examples. Firstly, consider the situation when the pressure outside the carriage rises to substantially more than that inside. The air flow rate through the intake increases, and the air flow rate through the exhaust decreases. The rapidly rising air flow through the intake bends the leaf spring against the limit switch 4 and so immediately shuts the shutter 6. The intake flow rate therefore drops to zero and the leaf spring 2 returns to its rest condition, opening the limit switch 4. However the timer 30 keeps the shutter closed for the predetermined period T₁. This period is relatively short, and the exhaust flow rate is small at this time. Accordingly, the substantial cessation of ventilation does not continue so long as to cause significant contamination in the passenger space. More importantly, the immediate cut off of the potentially excessive intake air flow prevents propagation of the high pressure into the car and hence prevents the possibility of discomfort to the passengers. From this, it will be appreciated that even a single ventilation control device as described e.g. in the intake, can give an advantage. As discussed in the fuller example given below, it is however normally desirable to have such a device for both the intake and the exhaust. Figure 10 shows three graphs having a common longitudinal time scale. The events are typical of those for the lead carriage of a train passing through a tunnel at very high speed e.g. about 300km/h. The top part of the Figure shows the pressure measured outside the carriage, and calculated for the interior by simulation for the train passing through the tunnel. Initially, the relative pressure at the outside rises to a high value of about 300mmH₂O and then falls again, over a period somewhat more than 15 seconds. The exterior pressure then drops very steeply to a relative pressure below -400mmH₂O. After that, it gradually returns to the normal level. The middle and bottom parts of the Figure illustrate the response of the ventilation control system. As the initial exterior pressurise occurs, intake flow rate rises steeply and within a few seconds meets the threshold value of 35m³/min. This triggers the limit switch 4 of the intake control device and the shutter 6 on the intake promptly closes the intake duct. The pressure inside the carriage rises by only a very small fraction of that outside. At this stage, the exhaust flow rate drops so that the exhaust duct is not closed but the reduced flow rate prevents any excessive pressure fall inside the carriage. Irrespective of outside pressure, the timer 30 of the intake device now holds the intake duct closed for the period T₁: set to about 15 seconds in this case. The solenoid 5 is then released and the return spring 8 opens the shutter so that air flow resumes through the intake duct. By this time the exterior pressure is not so extreme, so the resulting intake flow is below the threshold level T although still just above the rated flow RF. Accordingly both ducts remain open. The exterior pressure then drops steeply as described above. This causes a decrease in the intake flow rate, so the intake leaf spring does not actuate the shutter. There is however an immediate steep increase in the exhaust flow rate because of the low outside pressure, and the exhaust flow rate rapidly rises to the threshold value T and closes the shutter of the exhaust duct for a period T₁. In this case, the preset closure periods T₁ of the intake and exhaust devices are the same, although they need not necessarily be so. After 15 seconds, the solenoid 5 is deactivated and the exhaust duct is re-opened. But, the exterior pressure is still very low and the resulting full flow through the exhaust is still above the threshold level. Very quickly, the leaf spring hits the limit switch 4 again and the exhaust duct is re-closed after a short period T₂ e.g. 2 to 5 seconds corresponding to the time taken for the leaf spring 2 to operate. After another 15 seconds, the "sampling" is repeated: the exhaust duct is re-opened and flow resumed but the flow rate is still too high for passenger comfort and so the duct is promptly closed again. By the next re-opening, however, the exterior pressure is coming back up to normal and the exhaust flow rate drops below the threshold value T. The exhaust shutter therefore does not re-close and ventilation continues as normal. Reference to the top of Fig. 10 shows how this operation keeps the pressure fluctuation inside the carriage relatively small, despite the very large and sudden fluctuations occurring outside. Conditions are kept within regions " X " of Fig. 8, and the passengers do not feel discomfort. Advantages of the system described will readily be perceived. Firstly, the co-operating relationship of the leaf spring, shutter and timer obviates any need for a purpose-made pressure sensor and processing circuitry for continuously monitoring its reading and comparing the reading with reference threshold values. In the prior art, special low-voltage DC power sources were needed to run the sensor and control unit: in the present device these are not needed. Instead, the leaf spring itself serves as a continuous sensor with a reference value built into its own physical construction and the spacing from the switch actuator 4a. The spring sensor 2 is robust, and unlike known sensing circuitry it is not liable to interference from electrical noise and the like. Using the pre-set timer feature, this simple sensor can "sample" the air flow conditions periodically while maintaining a sufficient degree of isolation of the passenger space. The device described is also capable, unlike the prior art devices, of coping with the extreme pressure changes caused by extremely high-speed trains. A skilled man will appreciate that other embodiments are possible. For example, the leaf spring 2 is only one possibility for a flow sensing means. Fig. 11 shows another possibility, in which a rigid flap 2′ is mounted at a pivot 61 at the side of the duct, and moved against the restoring force of a tension spring 60 connected to a lug 62 fixed to the duct upstream of the flap 2′. An extra stop member 3′ is needed on the upstream side, to keep the flap perpendicular against the spring force. In the embodiment specifically described, a duct was closed only if flow rate through that particular duct was sensed as excessive. In another embodiment, there can be synchronous operation whereby detection of an excessive flow rate in either the intake or the exhaust duct would trigger the shutting of both said ducts.

Claims: A ventilating device for ventilating the interior of a high-speed carriage, comprising a shutter (6) for closing a ventilating duct communicating between the interior and the exterior of the carriage, and characterised by a sensing device having a movable element (2) subject to air flow between the interior and exterior of the carriage, and means (4,5) actuated by the sensing device only after a predetermined degree of movement of the movable element (2) thereof, to cause the shutter (6) to close the ventilating duct. A ventilating device according to claim 1 in which a said sensing device, shutter (6) and shutter closing means are provided for each of an intake duct (51) and an exhaust duct (53) of the carriage. A ventilating device according to claim 1 or claim 2 in which the movable element (2) of the sensing device itself contacts and actuates an actuating member (4a) of the shutter-closing means (4,5). A ventilating device according to any one of claims 1 to 3 comprising means (30) for re-opening the shutter (6) at a predetermined interval after closing. A ventilating device according to any one of the preceding claims in which the movable element of the sensing device comprises a deflectable flap (2) disposed in the ventilating duct. A ventilating device according to claim 5 in which the flap (2) is a leaf spring. A ventilating device according to claim 5 comprising a separate restoring spring (60) against which the flap (2′) is moved by the air flow. A ventilating device according to any one of the preceding claims, further comprising a blower (50,52) for driving air through the duct. A train carriage having a ventilator system comprising an intake blower (50) for blowing air from the exterior to the interior of the carriage through an intake duct (51), and an exhaust blower (52) for blowing air from the interior to the exterior of the carriage through an exhaust duct (53); characterised in that air flow sensing devices are provided in the intake and exhaust ducts (51,53), comprising means (2,4) for determining when air flow therein reaches a predetermined threshold value, and in that shutters (6) are operatively connected to the sensing devices and operated, so as to close off air flow through the ducts, only when the air flow threshold value is reached. A carriage according to claim 9 in which the shutters (6) and sensing devices operate using only AC power. A carriage according to claim 9 or claim 10 in which a shutter-operating means (4) is electrically operated, and protection means (24,29) are provided which, in the event of a defect of the shutter-operating means (5), cut off electric power from both the shutter-closing means (5) and the respective blower. A carriage according to any one of claims 9 to 11 in which the air flow sensing devices comprise movable elements (2) subject to air flow in the ducts (51,53), the movable elements (2) being spaced from respective switching elements (4a) which are actuated by the moveable elements after a predetermined degree of movement thereof, to switch the shutters (6) to the closed condition. A carriage according to any one of claims 9 to 12 in which the switching element (4a) is contacted and actuated by the movable element (2) itself. A carriage according to claim 12 in which the movable element (2) is a flap disposed extending across the respective duct and movable against a restoring force. A method of ventilating a high-speed carriage in which an intake blower (50) blows air from the exterior to the interior of the carriage through an intake duct (51), and an exhaust blower (52) blows air from the interior to the exterior of the carriage through an exhaust duct (53), characterised by contacting air flow in the exhaust and intake ducts against respective movable sensing elements (2); shutting off a respective one of said ducts when the degree of movement of the movable element (2) therein reaches a predetermined value, and holding said duct in the shut off condition for a pre-set time period, and then re-opening said duct to allow resumption of air flow. A method according to claim 15 in which the pre-set time period is at least ten seconds. A method according to claim 15 or claim 16 in which a shutter (6) for shutting off a duct is not actuated to shut off the duct until the movable element (2) reaches said pre-determined degree of movement. A ventilating device for a train carriage, comprising a duct (51,53) and a fan (50,52) for blowing air through the duct; a shutter (6) movable to close the duct, and means (5) for driving the movable shutter (6), and a movable flap (2) extending across the duct so as to be moved against a restoring force under the influence of air blowing through the duct, in which the movable flap (2) actuates the shutter-driving means (5) at a predetermined degree of movement of said flap (2). A ventilating device according to claim 18 in which the flap (2) is mounted for swinging movement in the duct. A ventilating device according to claim 18 or claim 19 in which, at the predetermined degree of movement of the flap (2), the flap contacts a limit switch (4,4a) positioned in the path thereof to actuate the shutter-driving means (5).

Inventors: HIGAKI HIROSHI, HIRAKAWA HARUO, IKIO ATSUSHI, ISHIKAWA SHINICHIROO, MATSUMOTO MASAKAZU, HIGAKI, HIROSHI, HIRAKAWA, HARUO, IKIO, ATSUSHI, ISHIKAWA, SHINICHIROO, MATSUMOTO, MASAKAZU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1992
Main classification: B61D27
IPC codes: B61D27