GB2184405A - Trailers - Google Patents

Abstract

The platform of a trailer, fitted with leading or trailing arm type suspension and having compressible fluid springs acting between the arms and the trailer, rises and falls during loading and unloading. If the brakes are applied there is also fore and aft movement of the platform. These movements are substantially eliminated by providing for deflation of the springs before the brakes are applied. The trailer supply line 2 is pressurised from the tractor (not shown). It opens valve 51, closes valve 55 and maintains the automatic brake off via the relay emergency valve 3. Operation of dump valve 57 allows air under pressure from reservoir 13 to operate valve 26 connecting air springs 22, 23 to atmosphere via valve 51. Removal of pressure from line 2 allows reversion of valve 51 to isolate the air springs and to allow application of the automatic brake. Valve 55 also changes over to allow re-setting of dump valve 57 to permit reversion of valve 26. <IMAGE>

Description

SPECIFICATION Trailers This invention relates to a trailer having the following features. Road wheels are connected to the trailer body by way of pivotal leading arm or trailing arm type connections. The arm type connections may be rigid or resilient, for example comprising leaf springs. Compressible fluid spring means act between said arms and the trailer body. The trailer is equipped with fluid pressure operated parking brake and/or automatic brake equipment and a compressible fluid control system for application/release of the parking and or automatic brake and inflation/deflation of the air springs. The brake equipment may function so that the automatic brake is applied by application of fluid pressure and the parking brake is applied by decay of fluid pressure, for example a spring operated brake or by manual/mechanical actuation.

Such a trailer will hereafter be referred to as a trailer of the type described.

When a trailer of the type described is at a loading bay to be loaded or unloaded problems have been encountered in that, as loading or unloading progresses, the trailer platform height changes due to changed loading on the air springs causing them to compress or allowing them to extend. This occurs due to the progressive change of load as the load borne by the trailer changes and also due to the movements of, for example, a fork lift truck onto, over and off the trailer platform whilst effecting the loading or unloading of the trailer. Normally the tractor will be disconnected and consequently, as required by law, the trailer parking brake will be applied during loading and unloading. Since the wheels will be locked the pivotal movement of the leading or trailing arms will cause fore and aft movement of the trailer platform.Both the vertical and longitudinal movements of the trailer body are undesirable and can be dangerous.

The up and down movement of the trailer platform can be minimised by arranging to deflate the air springs so that the arms rest on the bump stops before loading/unloading commences. However, this alone will not eliminate the objectionable fore and/or aft movement.

According to the present invention in a trailer of the type described means are provided to prevent deflation of the air springs unless a pressure air supply is connected to the trailer from a tractor or other source.

Means may be provided to delay application of the parking brake whilst the air springs deflate or may prevent application of the parking brake until the air springs are deflated.

Means may be provided to effect release of the parking and or automatic brakes before the air springs can be inflated. Such means may prevent inflation of the air springs unless the parking brake/automatic brake is released.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic circuit diagram of a compressible fluid control system for a trailer wherein the automatic brake is operated by the application of pressure fluid to the brake actuator, Figure 2 is a schematic circuit diagram of a compressible fluid control system for a trailer wherein the parking brake is operated on decay of fluid pressure, Figure 3 is a schematic circuit diagram of an alternative compressible fluid control system for a trailer wherein the automatic brake is operated on decay of fluid pressure in the supply line and showing the fluid connections made when the trailer is coupled to a tractor and in the running mode Figure 4 is similar to Figure 3 but shows the fluid connections made when the trailer air suspension is deflated, and Figure 5 is similar to Figure 4 but shows the fluid connections made when the trailer is uncoupled from the tractor Referring to Figure 1, the trailer is connected to a compressible fluid pressure source on a tractor (not shown) by a conventional two pipeline system, of which pipe 1 is the trailer control line and pipe 2 is the trailer fluid pressure supply line. Control line 1 is connected to the usual relay emergency valve 3.

The latter is connected to supply line 2 via a 2-position 3-way pilot operated spring return valve 4 and pipe 5. Outlets from valve 3 are connected by pipes 6, 7 to brake actuators 8, 9 for the wheel brakes on the trailer.

Depending on the number of axles and wheels there may, of course, be more than two brake actuators.

A brake reservoir 11, pressure protection valve 12, suspension reservoir 13, pressure limiting valve 14 and a 2-position 3-way spring return suspension dump valve 1 5 are connected in series to relay emergency valve 3 by pipes 16, 17, 18, 19 and 21. Air springs 22, 23 (only two are shown but the trailer may of course have more than two,depending on the number of wheels/axles on the trailer) are connected to pipe 19 via pipes 24, 25, a 2-position 3-way pilot operated spring return valve 26, pipe 27, levelling valve 28 and pipe 29.

The pilot connections of valves 4, 26 are connected to a 2-position 3-way pilot operated spring return valve 31 respectively via pipe 32, one way variable restrictor 33, pipes 34 and 35 and via pipe 36, one way variable restrictor 37, pipe 38 and pipe 35. Valve 31 is connected to valve 15 by pipe 30 and pipe 20 connects pipe 2 to the pilot of valve 31.

When a tractor is connected to the trailer the pipes 1 and 2 are pressurised from a fluid pressure source on the tractor. In conse quence valve 31 will be pilot operated into the open position wherein the pilots of valves 4, 26 are connected to atmosphere via their associated one way restrictors, valve'31 and valve 15. Valve 4 now connects supply line 2 to relay emergency valve 3 whereby reservoirs 11 and 13 may be charged. Valve 26 is open to allow air from supply line 2 to enter the air springs via the reservoir 11, pressure protection valve 12, reservoir 13 and levelling valve 28.

On operation of valve 15, for example manually or by electrical solenoid, pressure air from reservoir 13 is enabled to pass through pressure limiting valve 14, valve 15 and valve 31 to the one way restrictors 33, 37. As shown on the drawing, the pressure air is enabled to pass freely through restrictor 37 to the pilot of valve 26, operating valve 26, and causing the air in springs 22, 23 to be dumped to atmosphere. The flow through restrictor 33 is restricted and consequently there is a delay before the pilot operates valve 4 to shut off pipe 2 and connect pipe 5 to atmosphere. With loss of pressure in pipe 5 the relay emergency valve 3 operates to supply pressure air from reservoir 11 to brake actuators 8, 9 so causing the automatic brake to be applied.Restrictor 33 is adjusted to provide the necessary delay to allow the air springs 22, 23 to deflate before the automatic brake is applied. If the tractor connection to supply line 2 is now broken the valve 31 will revert, trapping pressure air in the system between valve 31 and valves 4, 26 so these remain in the operated position preventing release of the automatic brake and reinflation of the air springs from reservoir 13.

When loading/unloading is completed and it is desired to re-inflate the air springs it is first necessary to operate valve 31 in order to re lease pressure from the pilots of valves 4, 26.

This can only be done by re-connecting sup ply pipe 2 to a source of pressure fluid, for example on a tractor.

When valve 31 has been operated, and dump valve 15 has reverted under the bias of its sprinq, the pressure air can flow freely to atmosphere through one way restrictor 33 to allow valve 4 to revert, restoring air pressure supply to valve 3 and thereby causing the automatic brake to be released. However one way restrictor 37 delays reversion of valve 26 so ensuring the automatic brake is off before the air springs 22, 23 are re-inflated.

Referring now to Figure 2, components cor responding to those which have been de scribed with reference to Figure 1 have been given the same reference numbers. The features of this circuit which differ from those of Figure 1 will now be described.

The pressure limiting valve 14 is connected to pipe 18 by a pipe 41. A shunt valve 42, for example a manually operated valve, is con nected to supply pipe 2 by a pipe 43, to relay emergency valve 3 by a pipe 44 and to pipe 17 by a pipe 45. A 2-position 3-way pilot operated spring return valve 46 has its pilot connected to one way restrictor 33 by pipe 32. A park valve 47 is connected between pipe 45 and valve 46, and a pipe 48 joins valve 46 to the spring brake connections of brake actuators 8', 9' via a double check valve 49, quick release valve 49A and pipes 51, 52 respectively. Double check valve 49 is also connected to pipe 6.

When a tractor is connected to the trailer the control pipe 1 and supply pipe 2 are connected to a source of fluid (e.g. air) pressure on the tractor. Supply pipe 2 is connected to emergency relay valve 3 via shunt valve 42.

Supply pressure passes via reservoir 11, pipes 17 and 45 to the park valve 47 and thence through valve 46 and double check valve 49 to brake actuators 8', 9' to release the spring applied parking brakes. This is possible because valve 31 is actuated by supply pressure through pipe 20 to its pilot, thus venting the pilots of valves 26, 46 through dump valve 15 whereby valves 26, 46 revert to their normally open positions. The air springs 22, 23 can now be inflated as has been described with reference to Figure 1.

Operation of the park valve 47 will disconnect pipe 48 from supply pressure in line 45 and vent pipes 51, 52 via valve 46.

On operation of dump valve 15 supply pressure from reservoir 11 passes through protection valve 12, pressure limiting valve 14 and valve 31 to the one way restrictors 33, 37.

As before there is free flow to the pilot of valve 26 and this is operated to release the air from the air springs 22, 23. Flow to the pilot of valve 46 is restricted whereby there is a delay before this valve is operated to vent the spring brake chambers of actuators 8' 9' whereby the spring actuated parking brakes are applied. Thus the air springs are deflated before the parking brake is applied. Disconnection of the supply to pipe 2 causes reversion of valve 31 to its normally closed position whereby pressure is locked in to maintain valves 26, 46 in their operated positions.

On re-connection of the supply to pipe 2 the valve 31 is again operated, venting the pilots to valves 26, 46. The one way restrictors 33, 37 ensure that valve 46 reverts first whereby pressure fluid is applied to the spring brake chambers to release the parking brakes.

After a short interval the valve 36 reverts enabling the air springs to be re-inflated as has already been described.

It will have been observed that in each case the valve 31 prevents deflation of the air springs unless a pressure air supply is available to operate the valve 31.

It will be seen that the valve 31 in combination with the one way restrictors 33, 37 and valves 4, 26 (Figure 1) or valves 46, 26 (Fig ure 2) allow deflation of the air springs before the automatic or parking brakes are applied, whilst a pressure air supply is available at pipe 2. In the embodiments which have been described the delay in application of the brakes may be varied by adjustment of the restrictor 33. The adjustment made may be such as to prevent application of the brake until the air springs are deflated. However, it will be appreciated that this desired sequencing may be achieved in other ways. For example, a normally closed sequence valve could be fitted which is operated, for example by one of the arms, when the air springs have deflated so as to open a flow path between pipes 32 and 34.

This would replace the variable restrictor 33 and the one way function would be retained by substituting a similarly directed check valve. Such an embodiment would prevent application of the brakes until the air springs are deflated and ensure the brake is released before re-inflation of the air springs takes place.

The air springs 22, 23 can only be deflated when the valve 26 is in the operated position.

As has already been seen this can only occur when a pressure supply is available at pipe 2 to operate valve 31.

The valve 31 in combination with the one way restrictors 33, 37 and valves 4, 26 or 46, 26 ensure that release of the brakes occurs before the air springs can be inflated.

The adjustment made of the restrictor 37 may be such as to ensure that inflation of the air springs is prevented until the brakes are released.

During normal operation of the trailer the pipe lines to the pilots of valves 4, 26, 46, 26 are vented consequently a failure in any of these lines will not cause automatic/involuntary application of the brakes. Their pressure supply is derived from the reservoirs, or one of them.

The suspension and brake control circuits are interlocked with the pressure supply line such that the control is totally disabled if the trailer is separated from the tractor (or other source of fluid pressure supply).

It is important in the embodiments which have been described that when the air springs are deflated the pressure in the control lines to the pilots of valves 4, 26, 46, 26 should not decay before decay of pressure in the suspension reservoir 13 otherwise the springs could re-inflate and cause longitudinal movement of the trailer platform. To ensure this it may be arranged for the suspension reservoir to be vented when the air springs are deflated, for example by use of a modified valve 26 which, in the operated position, connects pipe 27 to atmosphere.

It will be appreciated that whilst a relatively large time delay requires to be imposed by the one way restrictor 33 to allow the air springs to deflate before the brake is applied only a relatively small delay may be required to be imposed by the one way restrictor 37 to enable the brake to be released before inflation of the air springs commences. It may be found that the pipes 38, 36 (depending on their length, configuration and bore) impose sufficient restriction, and hence delay, as to enable the one way restrictor 37 to be dispensed with.

The pressure limiting valve 14 has been included to reduce the pressure applied to the one way restrictors 33, 37 and thereby facilitate adjustment of the delay periods required.

If the required delays can be obtained using full system pressure then the pressure limiting valve 14 may be omitted.

Referring now to Figures 3, 4 and 5, the same reference numerals are used for parts corresponding to those of Figures 1 and 2.

The supply line 2 is connected to the pilot of a 2-position 2-way pilot operated spring return valve 51 by pipes 52, 53. Valve 51 is interposed between valve 26 and pipe 25, being connected to valve 26 by a pipe 54.

A 2-position 3- way double pilot operated valve 55 is connected between pipe 53 and a pipe 56 whose other end is connected to the pilot of a 2-position 3-way pilot/manually operated dump valve 57. One pilot of valve 55 is connected to supply line 2 by a pipe 58 and the other pilot is connected by a pipe 59 to pipe 61 which connects dump valve 57 to the pilot of valve 26. Dump valve 57 is also connected to pipe 19 via a pipe 62.

As shown in Figure 3 the trailer is coupled to a tractor and supply line 2 is pressurised whereby the automatic brake is held off. At the same time valve 5 1 is operated to connect reservoir 13 to air springs 22, 23 via pipe 19, levelling valve 28, pipe 27, valve 26, pipe 54, valve 51 and pipes 25, 24. Also, valve 55 is operated to close pipe 53 and to connect the pilot of valve 57 to atmosphere via pipe 56. Dump valve 57 connects the pilot of valve 26 and the other pilot of valve 55 to atmosphere via pipes 61 and 59. Thus the automatic brake is off and the air springs are inflated.

Turning now to Figure 4, the trailer is still coupled to the tractor, supply line 2 is pressurised and dump valve 57 has been operated. Control line pressure keeps the automatic brake off, valves 51 and 55 remain in their operated positions. Operation of dump valve 57 admits pressure air from reservoir 13 to the pilot of valve 26 to operate that valve and to the other pilot of valve 55-but without changing the state of that valve. Valve 26 thus connects the air springs 22, 23 to atmosphere via pipes 24, 25, valve 51 and pipe 54 and they deflate.

Considering now Figure 5, the trailer has been uncoupled from the tractor so supply line 2 is now at atmospheric pressure and consequently the automatic brake is applied, the air springs being in the deflated condition. Loss of supply line pressure to its pilot has resulted in reversion of valve 51 and similarly valve 55 has reverted because reservoir pressure is still maintained at its other pilot via dump valve 57.

On re-setting of dump valve 57 valve 26 will revert as its pilot becomes connected to atmosphere, as shown in Figure 3.

On re-connecting the tractor (or applying an external source of fluid pressure to supply line 2) the automatic brake is released and valves 51, 55 are operated to their positions shown in Figure 3 permitting reflation of the air springs 22, 33 via the reservoir 13 as has already been described.

In this case it is the valve 51 which prevents deflation of the air springs unless a pressure air supply is available in the supply line 2 to operate valve 51 and allows deflation of the air springs before the automatic brake is applied.

Claims (11)

1. A trailer of the type described wherein means are provided to prevent deflation of the air springs unless a pressure air supply is connected to the trailer fluid control system from a tractor or other source.

2. A trailer as claimed in claim 1 wherein means are provided to effect release of the automatic brake before the air springs are inflated.

3. A trailer as claimed in claim 2 having a spring operated parking brake and including means to effect release of the parking brake before the air springs are inflated.

4. A trailer as claimed in claim 1 or claim 2 wherein means are provided to allow deflation of the air springs before the automatic brake is applied.

5. A trailer as claimed in claim 4 having a spring operated parking brake and including means to allow deflation of the air springs before the parking brake is applied.

6. A trailer as claimed in any preceding claim wherein the means to prevent deflation of the air springs unless a pressure air supply is connected to the trailer fluid control system comprises a pilot operated spring return twoway first valve wherein the pilot is connected to said pressure air supply and the first valve in its pilot operated position connects the pilots of pilot operated spring return three-way second and third valves to a fourth valve, said fourth valve having three ways and being selectively operable to connect the pilots of said second and third valves either to a fluid pressure supply or to atmosphere and said second and third valves control application/release of the parking brake and inflation/deflation of the air springs respectively and in its spring return position said first valve disconnects the pilots of said second and third valves from the fourth valve.

7. A trailer as claimed in claim 6 including first and second one way restrictor means connected between the first valve and the pilot of the second valve and between the first valve and the pilot of the third valve respectively, said first restrictor means allowing free flow from and restricted flow to the pilot of the second valve and said second restrictor means allowing free flow to and restricted flow from the pilot of the third valve whereby said third and second valves are operated successively by their respective pilots and said second and third valves are reverted successively by their return springs when their pilots are connected to atmosphere.

8. A trailer as claimed in any one of claims 1 to 5 wherein the means to prevent deflation of the air springs unless a pressure air supply is connected to the trailer fluid control system comprises a pilot operated spring return twoway fifth valve with its pilot connected to said pressure air supply and said fifth valve connected so as to allow flow to and from the air springs when operated by its pilot and to prevent such flow in its spring return position.

9. A trailer as claimed in claim 8 including a sixth valve in circuit with said fifth valve to control flow to and from the air springs via said fifth valve, said sixth valve being a pilot operated spring return three-way valve which in its pilot operated position connects the fifth valve to atmosphere to allow deflation of the air springs and in its spring return position allows flow of pressure fluid to and from the air springs via the fifth valve when the latter is in its pilot operated position.

10. A trailer as claimed in claim 9 wherein the fluid control circuit includes seventh and eighth valves, said seventh valve being a three-way manual/pilot operated valve operable to connect a source of fluid pressure to the pilot of the sixth valve and to a first pilot of the eighth valve or to connect said pilot to atmosphere and said eighth valve being a three-way double pilot operated valve operable by its first pilot to connect the pressure air supply to the pilot of the seventh valve and in its second pilot operated position to connect the pilot of the seventh valve to atmosphere, said second pilot being connected to the fluid pressure supply whereby manual operation of said seventh valve causes pilot operation of said fifth valve to allow deflation of the air springs in the presence of the fluid pressure supply.

11. A trailer of the type described having a fluid control system substantially as described herein with reference to Figure 1 or Figure 2 or to Figures 3 to 5.