Patent Application
20070296267
A previous system incorporated a valve arrangement which did not permit the red line to be activated (i.e. brakes released until the yellow line was activated, the driver had applied the footbrake). The valve then remained in its operating position by air pressure in the red line. However, it is possible that if the red line becomes inoperable (for example, due to an accident or breakdown), it could be difficult or impossible to release the emergency braking system in order to move the trailer.
Accordingly, embodiments described herein provide a valve or valve assembly for inclusion in an emergency air supply line to the trailer braking system of an articulated vehicle. The valve or valve assembly has an air inlet, an air outlet, a closing member, operating means, and control means. The air inlet is connectable to an upstream side of the emergency air supply line. The air outlet is connectable to a downstream side of the emergency air supply line. The closing member is biased towards a closed position in which passage of air through the valve between the first air inlet and first air outlet is substantially prevented. The operating means opens the closing member. The control means is for retaining the closing member in an open position on receipt of an electrical signal. The signal is derived from an electrical braking system of the vehicle. Hereinafter, for convenience only, the air inlet may also be referred to as the “red inlet” and the air outlet as the “red outlet”, and the normal brake line as the “yellow” line.
As with GB2341662, when such a valve is included in the emergency air supply line to a trailer braking system, the emergency braking system is not deactivated automatically when the emergency line is connected, by virtue of the closing member being biased towards a closed position which prevents passage of air through the valve. Rather, the emergency braking system is deactivated only when the operating means are activated, e.g., by operation of the foot brake and, activation of service air supply line. This of course has the effect that the trailer is still braked when the emergency braking system is released. Thus the trailer cannot become free-wheeling when the emergency line is connected. Preferably, the emergency braking system can also only be deactivated if the control means is activated i.e. is receiving an electrical signal.
However, in GB2341662 the closing member is then retained in an open position by air pressure in the emergency line, to keep the emergency braking system in a deactivated state until the pressure in the emergency line is reduced e.g. by disconnection of the line.
By contrast, the present invention includes control means for retaining the closing member in an open position and these means are kept activated by an appropriate electrical signal even once, e.g. the foot/hand brake is released. This provides the advantage that the valve does not automatically close if the pressure in the red line falls for any reason, for example in an accident or breakdown. When the pressure in the red line falls, the emergency brakes are of course applied but, in the prior art, it could be difficult if not impossible to then subsequently release the emergency brakes, even temporarily. With the present invention, as long as the electrical supply has been maintained to the control means, it will be possible to release the emergency brakes by raising the pressure in the red line in the usual way, without necessarily having to apply the normal brakes first.
The valve may be included at any position along the emergency line, e.g. preferably on the trailer side. For convenience of retrofitting to existing vehicles, the valve can be included near the point at which the tractor unit and trailer sides of the line are connected when the tractor unit and trailer are coupled. As stated, the electrical signal is derived (directly or indirectly from an electrical braking system, such as an item of braking assistance equipment e.g. an ABS or EBS brake system. This has the further advantage that if for any reason the braking system is not working (i.e. not powered) the opening means cannot be operated and therefore the emergency brakes cannot be released. This provides an additional safeguard.
In practice, the ABS or EBS brake system receives a permanent power supply from the tractor unit i.e. there is an electrical connection (sometimes known as the ABS or EBS lead) between the tractor and trailer which needs to be connected in the same way that the red and yellow lines are connected when the tractor and trailer are coupled together. When the control means is mounted on the trailer side, since it derives its electrical power from the braking system as described, this means that if e.g. ABS/EBS lead is not connected then the control means will receive no power and the brakes cannot be released. In other words, if the ABS/EBS braking system has not been properly activated, the trailer cannot be removed. Clearly this is an important safety advantage.
When it is stated that the signal for the control means is “derived” from an electrical braking system of the vehicle, as stated above this “derivation” could be direct or indirect i.e. it is not necessary that the signal comes straight from some part of the electrical braking system. In some embodiments, as will be seen in the specific description below, power from a part of the electrical braking system is connected to a pressure switch is located in the yellow line of the system. Not only does this power the pressure switch, but it is a convenient place from which the signal can be taken to the control means.
Preferably, the control means requires a repeated, continuous, or substantially continuous signal in order to remain activated i.e. to retain the closing member in an open position.
Preferably, the valve also includes start means which are activatable to operate the operating means open the closing member) on activation of a foot or hand brake of the vehicle.
The start means are electrically operated, unlike the arrangement in GB2341662. The electrical supply which operates the start means may be taken from a pressure switch which is operated, for example, by pressure to the yellow (normal braking) line.
The start means may include opening valve means (which may be one way and the whole may be arranged so that when the start means is operated by a suitable electrical supply, the opening valve means open to permit air pressure to pass from the red line to the operating means. The operating means may be operated by suitable pressure and may remain operated as long as suitable pressure is applied. The operating means may incorporate a piston which is movable by pressure to operate the closing member, and thereby to open the closing member.
The valve may include a further pressure supply means connected to or connectable to the air outlet or the downstream side of the emergency air supply line. This further pressure supply means serves to permit pressure in the downstream side of the air supply line to be applied to the operating means in order to keep the operating means operating (i.e. keep the closing member open) during operation of the vehicle.
During normal operation of the vehicle, the foot or hand brakes will of course not be applied most of the time and therefore the start means will not be operational, since the start means will not be receiving an electrical supply from e.g. the pressure switch. Were it not for the further pressure supply means, there would therefore be no pressure being applied to the opening means in order to keep the closing member in the open position.
Preferably the control means also includes a control valve which in use connects the air outlet or the downstream side of the emergency air supply line to the opening means. While electrical power is supplied to the control means the control valve remains closed, thereby preventing pressure from escaping from the operating means. Thus even if the pressure in the downstream side of the emergency air supply line falls (and therefore the emergency brakes are applied) the control valve remains closed and the pressure remains applied to the operating means so that the closing member remains open. In this way, if pressure can be reintroduced into the emergency supply line (by various normal operating techniques), the emergency brakes can be released when necessary. However, if the electrical power to the control means has been removed (e.g. by switching off the ignition or removing the ABS plug, or lead), the control valve will have opened and pressure will have escaped from the operating means, thereby allowing the closing member to close. At that stage, the only way to release the emergency brakes will be to go through the normal start up procedure.
Preferably the control means prevents the operating means from operating the closing member if the control means is not activated i.e. if it is not receiving electrical power. This helps to prevent the brakes being released if, for example, the ignition is not on.
Preferably, the closing member includes a second piston movable in a second chamber of the valve, the second chamber lying between the red inlet and red outlet. More preferably, the red inlet and red outlet are spaced apart in the direction of movement of the second piston. When the second piston is in its closed position, this feature allows the red inlet and red outlet to be isolated by a seal between the second piston and a wall of the chamber.
Preferably the closing member is spring biased towards the closed position, more preferably by a compression spring.
Preferably, an actuator for the closing member is connected to the piston in the opening means, which may be slidable in a second chamber of the valve.
Desirably, movement of the actuator is imparted to the closing member via a link. More desirably, the piston and actuator are in line, movement being imparted by the link along that line. Alternatively, however, in some embodiments the link could be pivoted. It is also possible that movement of the actuator could be imparted to the closing member hydraulically.
The valve may include an override, operable (desirably manually) to move the closing member into the open position in case of failure of the actuator to do so. Such an override may be lockable, to keep the closing member in the open position. Such a feature allows the valve to be completely disabled, and the emergency braking system will then function as if no valve were present.
The valve may include a bypass which, when the closing member is in its closed position, allows air to escape from the trailer side (i.e. downstream side) of an emergency air supply line connected to the valve. Such a bypass eliminates the possibility that by moving very rapidly to its closed position upon initial reduction of pressure in the red line, the closing member may prevent sufficient reduction in pressure on the trailer side of the valve to activate the emergency braking system.
A bypass may be provided by configuring the valve such that when the closing member is in the closed position, the red outlet is in communication with an exhaust outlet. In such an embodiment, the closing member must of course prevent communication between either the red inlet or the red outlet and the exhaust outlet, when it is in the closed position.
From a second aspect, the present invention provides a system for safely deactivating an emergency braking system of a trailer an articulated vehicle, the system including:
an emergency air supply line, in which is fitted a valve as defined in the first aspect of the invention.
All these embodiments share the advantage that the emergency trailer braking system is not deactivated until the driver is in the tractor unit, so any free-wheeling of the vehicle is preferably prevented. The valve according to the first aspect has the added advantage that the service braking system is activated when the emergency braking system is deactivated. This is simple for the driver. There is the further advantage of the valve that it may very conveniently be fitted to the air supply lines of existing trailers.
In further aspects, the present invention provides tractor units and/or trailers fitted with valves or systems according to the first two aspects.
Although in the above aspects it has been stated that the signal for the control means is derived from an electrical braking system of the vehicle, in other aspects it is envisaged that the signal may be derived from elsewhere. In other words, all that matters is that there is an electrical signal (taken from anywhere) which is capable of activating the control means.
Embodiments of the present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:
In
In the following description, the valve is connected as described below to the red (emergency) and yellow (service) lines of an articulated vehicle. The function and operation of these lines is described in the introduction. However, in its broadest aspects, the invention is not to be construed as being limited to the valve thus connected. Furthermore, mechanical elements of the prior art valve described with reference to
The first chamber 2 has an inlet 14 and an outlet 16, which may be connected to the red line. The inlet 14 and outlet 16 will therefore be referred to as the “red” inlet and outlet. The valve includes connectors (not shown) adapted for airtight connection of the red inlet and outlet to corresponding connectors on the red line. Suitable connectors may for example include male and female threaded sleeves. The valve may be fitted on a trailer of an articulated vehicle.
The first piston 6 is biased by a helical compression spring 18 to a closed position, shown in
The second chamber 4 has an inlet 22 and an outlet 24, which may be connected to the yellow line. The inlet 22 and outlet 24 will therefore be referred to as the “yellow” inlet and outlet. Again, the valve preferably includes connectors adapted for airtight connection of the yellow inlet and outlet to corresponding connectors on the yellow line.
The second chamber 4 includes a stop 26 which prevents the second piston 8 from blocking air passage through the chamber between the yellow inlet and outlet. As shown, the stop 26 includes a projection from an end wall into the bore of the chamber, leaving an annular space 28 in the chamber around the projection. The yellow inlet and outlet communicate with the annular space. Additionally or alternatively, the second piston may contain a through-hole to prevent restriction of the air flow between the yellow inlet and outlet.
Seals 30 between the second piston 8 and a cooperating side wall 5 of chamber 4 substantially eliminate leakage of air past the second piston 8. Under pressure in the yellow line (as occurs when a driver of the articulated vehicle depresses the brake pedal in the tractor unit), the second piston 8 is therefore pushed away from the stop 26 towards the other end of chamber 4.
A rod 12 is longitudinally aligned with the direction of movement of the pistons 6, 8 in the chambers 2, 4, such that movement of the second piston 8 in the second chamber 4 away from stop 26 imparts movement to the first piston 6 in the first chamber 2, against the bias of the spring 18, towards an open position in which passage of air between the red inlet and outlet is permitted.
Once the first piston 6 has been moved to the open position in the first chamber 2, and air passage between the red inlet and red outlet is permitted, high air pressure in the red line maintains the piston in the open position, against the bias of spring 18, until such time as the air pressure in the red line drops, whereupon the spring moves the first piston 6 back to the closed position, as shown in
Because the valve prevents air passage between the red inlet and outlet when the first piston 6 is in its closed position, reconnection of the red line following disconnection does not immediately result in air being supplied from the tractor unit to an air tank in the emergency braking system of the trailer (see introduction above) to deactivate the emergency braking system. Rather, deactivation occurs only when the first piston 6 moves to its open position, which as described above depends on air being supplied along the yellow line.
Inside valve 1, the connection between inlet 22 and outlet 24 is controlled by a valve member (shown in
The valve chamber 11 is in fluid communication with a start means 7, which in this case consists of an electrically operated one-way valve, with the one-way valve portion being shown by item 8. The one-way valve connects the upstream portion of the red line 6 to the chamber 11. The electrical feed for the operation of the start (or opening) valve is derived from a pressure switch 9, via connection 14. Pressure switch 9 is incorporated in part of the ordinary braking system 10 i.e. the yellow line. When the ordinary braking system is operated i.e. pressure is increased in the yellow line 10, the pressure switch 9 is activated and the start valve 7 receives an electrical signal and opens. This permits pressure from the red line 6 to be communicated to the chamber 11 and therefore the main valve 1 to be opened.
The chamber 11 is also in fluid communication with a pressure supply means 3, which in this case is a one-way valve. This supplies pressure to the chamber 11 from the downstream side of the red line 5. Thus, in use, when the red line is pressurised, chamber 11 will also be pressurised regardless of the state of start valve 7, thereby keeping the main valve 1 open.
Finally, chamber 11 is also in fluid communication with control means 4, which in this case is an electrically operated valve connecting chamber 11 to the downstream side of red line 5. The control means 4 derives its electrical supply from any suitable part of the vehicle electrical system. As mentioned before, this may, for example, be direct from the ignition system or indirectly from a part of a vehicle braking assistance system. In this case, positive supply 12 is taken from the ABS braking system line, where it is connected to pressure switch 9. With both of the electrically operated switches, there are suitable connections to earth (or negative supply) marked with numeral 13. In this way, as long as control means 4 is receiving a suitable electrical supply, the valve remains closed (not as shown in
In sequence, the operation of an example of a braking system incorporating a valve according to the present invention would be as follows:
It will be noted that the trailer brakes cannot be released if:
The invention may include any variations, modifications and alternative applications of the above embodiments, as would be readily apparent to the skilled person without departing from the scope of the present invention in any of its aspects.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0426588.0 | Dec 2004 | GB | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/GB05/04548 | Nov 2005 | US |
| Child | 11759147 | US |
