This invention relates to load transportation by means of vehicles using ground effect to support part of the load.

There have been a number of proposals for easing the load on goods vehicles by taking up a large part of the load using ground effect with a skirt. However, these have had problems due to excessive escape of air from underneath the lower edges of the skirt which has necessitated the use of excessive air supplies in order to maintain the air cushion and provide sufficient support for the load. Other problems include significant wear of the base region of the skirt and some wear effects on the road.

The present invention seeks to obviate or reduce these above disadvantages.

According to the invention, a ground effect transport system comprises a plenum roof platform for location beneath a load carrying means, a skirt depending from the platform to form a plenum chamber with the platform, fan means on or in the platform for supplying air to the plenum chamber, wherein the skirt extends downwardly towards the ground surface and has a ground engaging arrangement in the form of a brush unit, the brush unit comprising bristles adapted for engagement with the ground surface and being carried by one end of a flap which is connected at the other end in cantilever fashion to the skirt.

Preferably the flap is arranged to enable the brush unit to move up and down relative to the skirt so as to enable the brush unit to follow the ground surface and to this end may be flexible.

The flap may be disconnectable from the skirt to enable replacement of the flap and the brush unit may be disconnectable from the flap to enable replacement of the brush unit. The skirt may have a "J" - shaped cross section and the flap may lie, at least in part, beneath the "U" part of the "J".

The flap may extend inwardly of the skirt.

The part of the skirt located over the flap may be perforated to enable air from the plenum chamber to act on the flap so as to push downwardly on the flap and hold the bristles of the brush unit in contact with the ground surface.

The flap may comprise a plurality of sections arranged around the periphery of the skirt to form a continuous flap with the adjacent sections of the flap being flexibly connected together so that the individual sections can move independently of each other and allow the brush unit to float on the ground surface.

The bristles of the brush unit may be angled backwards in relation to the intended direction of travel of the vehicle so that, in use, the bristles trail along the ground surface. The bristles may be angled at about 30 degrees to the vertical

The brush unit may have one or more seals extending in the general direction of the bristles.

The invention will now be described in greater detail by way of example; with reference to the drawings, in which :-

Figure 1 is a general schematic side view of a vehicle in accordance with one embodiment of the invention; Figure 2 is a rear view of the trailer of a semi-trailer for the vehicle shown in Figure 1 with the support framework for the skirt shown and the details of the wheel arrangements removed.

Figure 3 is an enlarged sectional side view of the skirt showing details of its construction;

Figure 4 is a side view of the bristles of the brush shown in figure 3;

Figure 5 is an enlarged side view of the attachment of the bristle unit to the cantilever flap;

Figure 6 is an enlarged sectional view of the bristle holding arrangements;

Figure 7 is an enlarged view of showing one arrangement of the bristle unit;

Figure 8 is a sectional view showing the method of jointing flap sections together, and

Figure 9 is a sectional side view of the lower part of the skirt showing a further arrangement of the bristle unit.

Referring firstly to figure 1 , there is shown schematically a vehicle 1 to which the invention is applied. The vehicle shown is a semi-trailer which is a vehicle having a cab unit 3 which is self contained and is supported on the ground by two steerable front wheels 5 and four trailing wheels 7 at the rear. The trailer portion 9 in this case is, for transit purposes, supported at its rear by wheels 10 and by a plenum chamber 11 defined in part by a skirt 13 and at its front end by the rear wheels 7 of the cab unit 3 over which the front end of the trailer extends. The arrangements so far described are known. However, as has been mentioned above, the previous proposals have never been very satisfactory because of excessive escape of air from the plenum chamber due, to a large extent, to the construction of the plenum chamber and particularly of the skirt.

The application of the invention to the above described semi-trailer vehicle will now be discussed in connection with figures 2 and 3. Looking first at figure 2, there is shown a rear view of the trailer 9 of the semi-trailer 1. In this figure, the skirt arrangement is sectioned so as to indicate how the skirt is located.

Thus, the trailer 9 comprises a load carrying platform 21 which is basically supported towards its rear end by the six wheels 10 and at its forward end, when not connected to a cab unit 3 (figure 1) by means of loading legs (not shown). When attachment is made to the cab unit 3, the trailer 9 is connected as usual to the cab unit 3 by means of a king pin. In this situation, the landing legs are folded up towards the load supporting platform 21. ~

Attached to the loading platform 21 and depending therebeneath is a framework comprising two longitudinally extending "I" beams 23 from which the plenum chamber 11 is suspended by a pair of suspension connectors 25. As can clearly be seen from figure 2, the plenum chamber 1 is located inboard of the rear wheels 10 of the trailer 9 so that the wheels 10 are fully accessible. The "I" beams 23 sit above the wheel axles using a system of air bags 26 between the axles and the Ί" beams 23. Thus the plenum chamber will extend for a suitable distance above the ground generally in a range from 25.4 cm (10 inches) to 45.72 cm (18 inches) but with a preferable distance of 35.56 cm (14 inches).

The plenum chamber 11 comprises a plenum roof platform 27 extending over the whole area of the plenum chamber 1 and is the same shape as the plenum chamber 11. The skirt 13 is continuous and unbroken around the entire periphery of the plenum chamber 11. One or more fans for providing the air supply to the plenum chamber 11 are mounted on the plenum roof platform, one of these being shown in Figure 2 at 31. Usually there will be two fans, these being located spaced along the length of the plenum chamber. However, if desired, a single fan could be used situated at either end of the plenum chamber. Any other suitable formations of the fan can be used

Figures 3 to shows the construction of the skirt 13 and its attachment to the plenum roof platform 27. As can be seen, the skirt 3 has a cross section shape of a "J" or a mirror image thereof depending on which direction it is being looked at. The upper part 33 of the straight leg 35 is attached to the edge of the plenum roof platform by a connecting arrangement 37 in the form of a fixing plate fastened to the chamber structure by nuts and bolts by means of which the skirt 13 makes an airtight seal with the plenum roof 27. The skirt 13 is preferably made from extruded polyurethane. Preferable values for this material are

Hardness 90 Shore

Density ,250 kg/m ³

The "U" part 41 of the "J" is the part of the skirt 13 which approaches the ground surface 43 and is provided with ground engaging arrangement 61 in the form of a cantilever flap 63 removably attached at one end to the skirt by means of a pair of bolts 65. At the other end of the flap 63 is mounted a brush unit 67 providing a brush surface 44 which is in engagement with the ground surface 43. Various constructions of the brush unit will be described hereafter. However, it is to be noted that, in all the constructions described hereafter, material suitable for construction of the brush bristles includes PBT polyester, Polyvinylchloride and nylon. Suitable lengths for the bristles are 20 to 30 mm. The flap 63 is suitably constructed from the same material as the skirt, namely extruded polyurethane and is flexible so that the brush unit 67 floats on the ground surface 43 so that the skirt 13 is maintained above and out of engagement with the ground surface 43 while the brush unit 67 follows the contours of the ground surface 43. The part of the skirt 13 which overlies the flap 63 is provided with perforations 69 so that air from the plenum chamber 11 pushes downwardly on the flap 63 to push the brush unit downwardly so that it engages the ground surface with a predetermined force.

The skirt 13 basically comprises a top substantially rigid portion 33 which terminates in an inwardly extending strengthening rib 45 which extends longitudinally of the skirt 13. Inside of the strengthening rib 45 is provided a aperture, and a wire, rod or tube 47, suitably of steel, is provided therein. Sections of the rod 47 are suitably connected at their ends to provide a continuous rod which rod extends around the periphery of the plenum chamber 11. Below the strengthening rib 45 is a section 49 which is flexible and ends in a second strengthening rib 51 which also contains a strengthening wire rod or tube 53 also suitably of steel. The positions of the two strengthening ribs 45 and 51 are retained in position by anchoring lines 55 and 57 which, while permitting the skirt to move inwardly of the plenum chamber 11, prevents their movement outwards. These anchoring lines may comprise steel wire steel chain or steel rods. The anchoring lines 55 are anchored to plates 54 depending from the plenum roof 27 while the anchoring lines 57 are anchored at their other ends at 59 and 61 (see figure 2) to the plenum roof 27. The angle between the anchoring lines 55 and 57 and the straight leg 35 of the skirt 13 must lie at 90 degrees for the upper anchoring lime 55, and in the range of 10 to 50 degrees for the lower anchoring line 57, more preferably in the range of 10 to 40 degrees. For optimum results it has been determined that the best angle range for the lower anchoring line 57 is 20 to 30 degrees. The anchoring lines should be located at a spacing of no more than 1,000 mm but for maximum effect, this spacing should be reduced, for example, to 350 mm. With these anchor angles, a suitable positioning of the anchoring attachments and thus of the strengthening ribs is 18% down of the free depth of the skirt for the upper anchoring line 55 and 93% for the lower anchoring line 57. One form of brush unit can be seen from figure 4. Here the brush unit 67 comprises a base portion 71 from which bristles 73 depend. As can be seen, the bristles 73 are angled relative to the intended direction of travel 75 of the vehicle so that they trail along the ground surface 43. Suitably this angle may be in the region of 30 degrees to the vertical. In this particular embodiment of the brush unit 67, it is provided with a strip of sealing material 77, such as a thin strip of polyurethane, to ensure that the brush unit makes a generally airtight seal between the skirt 13 and the ground surface 43. With a bristle length of 20 to 30 mm., a strip depth of 10 to 15 mm. is suitable. The brush unit 67 is, of course, connected to the flap 63 as shown in figure 3. It will of course be appreciated that the inclination of the bristles is dependent on the direction of travel of the vehicle and that therefore the inclination direction in relation to the skirt will be different for the font and rear sections of the skirt to that of the side sections.

As the vehicle travels along the road, the skirt 13 will maintain a generally stable position while the brush unit 67 will move up and down following the undulating terrain of the road surface 43. Because the skirt is flexible, it is also able to ride over obstructions which are too large to be accommodated by the ground engagement arrangement 61.

It is important for a full satisfactory operation of the skirt and thus of the invention that the angles of the ties remain in these ranges. This will insure that air leakage is kept to a minimum so as to provide the desired lift to the vehicle with a minimum use of power to generate the necessary pressure in the plenum chamber.

Figure 5 shows a second embodiment of the brush unit 67. Here the brush unit 67 is mounted on a metal framework 81 which is attached to the free end of the flap 63, suitably by a pair of nuts and bolts 83. Thus the brush unit can be readily replaced without the need to replace the flap as well. Figure 6 shows schematically the construction of a third embodiment of brush unit 67. Here the brush unit comprises a block 87 with holes 89 in which the bristles 73 are secured at an angle of 30 degrees, to the vertical. The arrow 91 indicates the intended direction of vehicle travel. A thin polyurethane screen 93 is also secured to the block 87 for the purpose of providing additional sealing but it must be borne in mind that this orientation of the bristle angles to the screen is only suitable for side parts of the skirt, the bristle angle being adjusted for front and rear p[arts of the skirt. With a bristle length of 20 to 30 mm., a screen depth of 10 to 15 mm. is suitable.

Figure 7 shows schematically the arrangement of the brush unit 67 in a fourth embodiment. Here the brush unit comprises a metal frame 95 by means of which the brush unit 67 is attached to the flap 63 by any suitable means (not shown). The brush unit 67 is formed of three separate bolted together brush elements 97 with the middle element separated from the adjacent element by a thin polythene sealing screen 99 which assists in the sealing of the skirt to the ground surface. An outer sealing screen 99a is also provided. With a bristle length of 20 to 30 mm., a screen depth of 10 to 15 mm. is suitable.

Figure 8 shows that the flap 63 is formed of a number of sections, two of which are shown at 63a and 63b which extend right around the periphery of the skirt 13.. The lengths of the individual flap sections, i.e, the distance between the skirt and the brush unit, are between 10 and 20 cms with the thickness of the flap sections being between 10 and 12 mm. The circumferential length of the flaps is between 1/2 and 1 metre. The flap sections are constructed from polyurethane material which is preferably the same material as that of the skirt 13 itself. The brush units 67 are provided in the same lengths as the flap sections. So that the flap sections are individually and independently movable vertically to take account of variations in the ground surface, and so that a seal is maintained between them, the individual sections are joined together by a flexible material 01 which spans the gap 103 between the flap sections Figure 9 shows a variation of the with ground engaging arrangement 61. Here the flap 63 is attached to the skirt 13 by a single nut and bolt arrangement 103, as opposed to the double arrangement 65 shown in figure 3, making replacement of the flap 63 easier. Also, an additional sealing screen 105 is provide on the outside of the brush unit 67. With a bristle length of 20 to 30 mm., a screen depth of 10 to 15 mm. is suitable.

It is to be understood that the various embodiments of the invention shown can be used together or in replacement for each other. Thus, the use of inclined bristles as discussed in connection with figure 4 can be used for the bristles shown in figures 3 , 5, 6, 7 and 9. The joining arrangements of the flap sections as described in connection with figure 8 can be used for the flaps used in all other embodiments.

It will be appreciated that various modifications of or additions to the above described embodiments may be made without departing from the scope of the invention. For example, in certain circumstances, it may be desirable that, instead of locating the skirt inside of the wheels, it could be located outside the wheels, leaving the wheels located in the plenum chamber.

In addition to the air supply provided by the fan, additional air can be provided using a ram air intake facing forwards above the cab unit

In another possible modification, the plenum chamber could be constructed to be readily removable so that it could be transferred from one vehicle to another.

It will further be noted that while the invention has been described in connection with a semi-trailer, it could also be applied to both full trailers and articulated or other types of lorries. It could also be used on other land vehicles such as trains, coaches or buses.