The present invention concerns a method to modify the rear assembly of a vehicle of light self-supporting type and provided with a body, whereby its rear assembly demonstrates a rigid transverse rear axle that is suspended in a sprung manner relative to the body by means of spring means, which are arranged at each end of the rear axle. The invention concerns also an arrangement for the execution of the conversion of a vehicle.

The conversion of front-wheel-drive standard vehicles by lowering a part of the floor in order to increase the accessibility of the vehicle for, for example, people who use wheel- chairs is known. This type of conversion is common for light transport vehicles for the transport of goods or passengers, i.e. vehicles of weight up to approximately 3.5 tonne. The term "vehicle of self-supporting type" is here used to denote that type of vehicle whose chassis, body and beams are mounted together to form one unit. This is to be contrasted with "framed vehicles", which have a separate supporting frame with a body suspended from it.

The converted vehicle must demonstrate sufficient distance between the floor and the internal roof such that the vertical space required for, for example, a person using a wheel-chair is created, as is also the width that is required for the wheel-chair. Furthermore, it is desired that the lowered floor in the vehicle be horizontally plane, i.e. not sloping, and that it demonstrate a low instep or threshold. Based on these requirements, it is normal that the type of vehicle known as a "van" is used for this type of conversion. Such vans are provided at the rear with one large hatch or a pair of doors that can be opened. By removing the existing suspension of the van with its transverse wheel axle that stretches under the vehicle and replacing this by a separate suspension that is located on each side of the central line of the vehicle and replacing this by two separate suspensions that are located one on each side of the central line, it is possible to lower a central, principally rectangular, portion of the floor by it being given the shape of a box. This box is united with the existing body of the vehicle through welding. The term "suspension" is here used to denote the system of springs, shock absorbers and swivel arms that links the chassis of a vehicle to its wheels. A support arm is part of each such suspension that extends essentially parallel with the longitudinal direction of the vehicle from a first forward attachment to a transverse beam of the frame of the vehicle to a second attachment at the wheel holder. The possibilities of forming a lowered floor surface with the dimensions required with respect to length and width are limited by stiffening beams that lie transverse across the body of the vehicle. It should be realised in this respect that support arms that are of a length that is too great, positioned on each side of the lowered floor, do not offer an optimal compression ratio for the shock absorber and spring that are arranged in connection with the wheel holder, and that long support arms can contribute to an undesired phenomenon known as "self-governance" through the appearance of instability.

In order to limit the lengths of the support arms, the floor is arranged with a slope upwards towards the existing transverse beam that is a part of the chassis and in which the support arms are fastened in a manner that allows pivoting, whereby the said transverse beam extends under a forward portion of the lowered floor. A sloping floor of this type makes it more difficult to roll in a wheel-chair into the vehicle and it furthermore means that the distance between the floor and the internal roof, and thus also the available space, is reduced in the direction from the opening of the rear assembly and forwards in the vehicle.

US 7,641 ,209 B2 reveals an arrangement for the conversion of light vehicles that comprises two separate suspensions, one on each side of the central line of the vehicle, intended to replace the existing suspension of the vehicle such that a box-like central portion of the floor, essentially having a rectangular form, can be arranged between the said separate suspensions. The arrangement comprises a subframe that is intended to be fixed to the existing chassis of the vehicle in a conventional manner through, for example, welding or by means of screw fixings. The subframe is built up from a combination of a number of longitudinal and transverse beams that are arranged in a common plane and that are distributed at mutual distances from each other along the length and width of the vehicle. In order to form a space for a box-like lowered portion of floor, a number of the transverse beams are formed as yokes and demonstrate a pair of vertical downwardly directed shanks, the free ends of which are mutually united with horizontal transverse webs intended to form a support plane that supports the lowered portion of floor at a level that is located somewhat below the principal plane of the subframe. The separate suspensions are arranged at the side of the outermost longitudinal beams of the subframe whereby the forward end of a support arm that is a component of the relevant suspension has its forward point of attachment in a relatively short section of beam that protrudes in a sideways direction from the outermost longitudinal beam of the subframe. One problem with the known arrangement is that its framework structure with an extensive network of longitudinal and transverse beams limits the possibilities of forming a plane floor surface with the surface area required with respect to both width and length, and the possibilities of achieving a lowered floor with the required low instep are also limited due to the transverse sections of beam on which the lowered floor rests.

A first purpose of the present invention, therefore, is, to achieve, based on prior art technology, a method to modify the rear assembly of a vehicle of lighter type such that a considerably more extensive and larger inner space that previously is obtained without deviating from the requirement that the rear assembly of the vehicle shall demonstrate high stability after the modification. A modification of the rear assembly of the type of vehicle described in the introduction can be carried out both simply and cheaply. A second purpose of the invention is to achieve an arrangement for the conversion of a front-wheel-drive light vehicle that increases the applicability of the vehicle for different transport operations and that makes the vehicle more accessible for people who use wheel-chairs. A third purpose of the invention is to achieve an arrangement for the conversion of a front-wheel-drive vehicle that makes it possible to achieve a lowered portion of floor with an extensive surface area with respect to both width and length, in which it is not necessary for this portion of floor to be arranged sloping upwards from the opening of the rear assembly, but that can instead be arranged fully plane parallel with the bottom plate of the vehicle. A fourth purpose of the invention is to achieve an arrangement that allows a lowered floor surface that demonstrates a very low instep.

These aims of the invention are achieved through a method that demonstrates the distinctive features and characteristics that are specified in claim 1 , and, with respect to the arrangement, through the distinctive features and characteristics that are specified in claim 4.

Due to the fact that the subframe and its associated separate suspensions demonstrate a yoke-shaped or U-shaped frame with two parallel longitudinal frame beams and a transverse frame beam, where each support arm in the relevant separate suspension has its first forward point of attachment located at a position under a longitudinal frame beam and, attached to this frame beam, extending backwards parallel with the longitudinal beams under it, a space of significant width is defined, contained between the two separate suspensions. A lowered floor with a very low instep is obtained through the subframe lacking transverse sections of beam under the lowered floor. Furthermore, very compact separate suspensions are obtained that do not encroach upon the space that is required for the formation of the box-shaped floor lowering. It can, finally, be pointed out that, through the support arms being arranged such that they can pivot on the subframe at a level in the vertical direction that is located below the principal plane of the subframe defined by the two outermost longitudinal frame beams, a box-like construction demonstrating a transverse gable wall, a pair of longitudinal side walls and a principally rectangular bottom, the inner surface of which is intended to form a lowered portion of floor at the chassis, can be made considerably wider than is possible with the prior art technology.

Terms such as "inner" and "outer" will be used below. These refer to equivalent directions, with reference to the longitudinal centre line of the vehicle unless otherwise stated. The same is true for the terms "forward" and "rear", which refer to the normal direction of travel of the vehicle. It should also be understood that, even if the embodiment that is shown below is described with welding taken as an example of the method of connection, it should be realised that other methods of connection known to one skilled in the arts can be applied, for example bolting, riveting and similar methods, without deviating from the invention.

Further advantages of the invention are made clear by the non-independent claims.

The invention will be described below in more detail in the form of embodiments with reference to attached drawings, of which:

Figure 1 shows in a perspective view a part of a rear assembly for a light vehicle that through conversion has been equipped with a lowered portion of floor, and a ramp from the support surface that slopes relative to the vehicle and is used to facilitate, for example, a wheel-chair being rolled into and out of the vehicle,

Figure 2 shows a perspective view of a part of the suspension according to the invention in a region behind the left rear wheel of the vehicle in Figure 1 ,

Figure 3 shows a side view a subframe that is a component of the arrangement with its associated suspension intended to be mounted on the existing chassis of the vehicle during the conversion,

Figure 4 shows a plan view from above of the subframe shown in Figure 3, and its associated suspension,

Figure 5 shows a view from the rear of the subframe shown in Figure 3, and its associated suspension,

Figure 6 shows a perspective view of the subframe with certain of the parts that are components of the suspension removed.

With reference to Figure 1 , there is shown the rear part of a rear assembly of a light vehicle 1 that has been equipped with a lowered portion of floor 10 through the normal transverse wheel axle of the vehicle having been removed together with the suspension and replaced by an arrangement according to the present invention. A ramp 11 is arranged sloping upwards towards the instep of the portion of floor 10, in order to facilitate, for example, a wheel-chair being rolled into and out of the vehicle. The existing suspension of the vehicle 1 has been replaced by two separate suspensions 14, one on each side of the central line of the vehicle. A central and principally rectangular portion of the floor has been lowered and formed as a box-like construction generally denoted by the reference number 15 and demonstrating a transverse gable wall 16, a pair of longitudinal side walls 17 and a principally rectangular bottom 18, the inner surface of which is intended to form the said lowered portion of floor 10 at the chassis. This box construction is united with the existing body of the vehicle through welding.

A part of the converted rear assembly is shown in more detail in Figure 2 equipped with a subframe 20 that is a component of the arrangement according to the invention. The subframe 20 will be described in more detail below and includes a principally yoke-shaped or U-shaped frame with two parallel frame beams 22 that extend in the longitudinal direction of the vehicle 1 and a transverse frame beam 24 that unites these (see Figure 6). Two separate suspension structures 26, one on each side of the vehicle on opposing sides of its central line, are present for the absorption of forces associated with the vertical spring motion of the wheel 25. Each suspension structure 26 comprises a support arm 27 that extends in the longitudinal direction of the vehicle and that is attached in a jointed manner at a forward end 28 with a joint 29 in the subframe. The spring facility that is a part of each suspension structure 26, one on each side of the vehicle, comprises a shock absorber 30, an air bellows 31 and a stop means 32 that can be deformed and that is intended to absorb impacts. The shock absorber 30 has a lower end 33 that is attached in a jointed manner at a rear end 34 that is a part of the support arm 27. The shock absorber 30 has furthermore an upper end 36 that is attached in a jointed manner with a fixture in the longitudinal frame beam 22 of the subframe. The air bellows 31 is located between an upper fixture 38 in the longitudinal frame beam 22 of the subframe and, resting on a lower fixture in the rear end 34 of the support arm 27, immediately in front of the attachment of the shock absorber to the support arm. The air bellows 31 is located immediately behind the centre C of rotation of the back wheel 25. The support arm 27 is provided with a wheel bearing housing 40 that supports in turn a hub 41 with a spindle, at which the said wheel 25 is mounted in a manner that allows rotation. The wheel bearing housing 40 supports further brake arrangements not only for travel but also for parking (not shown in the drawings). It is appropriate that the joints be designed as horizontally mounted bodies 42 including elastic material, the principal axial direction of which lies in the longitudinal direction of the vehicle 1. The elastic material in the joints may be constituted by rubber in order to dampen vibration. Through the use of air bellows 31 , the distance between the support surface and the body of the vehicle can be held constant and independent of the load, while regulation of the height of the chassis within a large interval is allowed and can, through suitable choice of components, be reduced such that the distance between the inner surface of the lowered portion of floor 10 and the road surface becomes approximately 240 mm or lower. Furthermore, the vehicle with the new spring facility can be raised approximately 70 mm above the normal driving condition, and the ability to proceed when the road conditions are poor is in this way improved. The arrangement increases comfort due to the fact that the rear assembly has two individual suspensions, one on each side of the central line of the vehicle.

With reference to Figures 3-6, the principally yoke-shaped or U-shaped frame that is part of the subframe 20 consists of two parallel longitudinal frame beams 22 extending backwards in the longitudinal direction of the vehicle, and a transverse hollow frame beam 24. As is made most clear by Figure 3, the U-shaped subframe 20 has its open part facing backwards. The transverse frame beam 24 is located in that part of the subframe that faces forwards in the direction of travel of the vehicle and demonstrates ends that are limited by suspension plates 50 that are set transverse relative to the frame beam 24. The transverse set frame beam 24 is united with the suspension plate 50 at its lower part by welding. The suspension plates 50 are provided at their tops with indentations 52 with which it is intended that one of the existing transverse beams 53 of the vehicle 1 , suggested in the drawing by a dash-dot contour, be placed to give an interaction that exerts control, and the suspension plates further have a number of weld holes 54 for the mounting of the suspension plates at the existing body of the vehicle through welding.

As is made most clear by Figures 3 and 6, an existing transverse beam 53 of the vehicle at which the indentations 52 of the suspension plates 50, and thus also the complete subframe 20, have been inserted will be located essentially directly above the transverse beam 24 of the subframe such that a gap 55 is created between the said parts, through which it is possible for, for example, exhaust pipes or similar equipment to pass (see Figure 2). Each one of the parallel frame beams 22 is formed from an extended piece of sheet metal with a principally L-shaped or U-shaped open structure and that, extending in the longitudinal direction of the vehicle, is attached onto the outer surface of the relevant suspension plate 50 by welding. Each one of the extended pieces of sheet metal is provided backwards in places along its complete length with portions 56 that, folded relative to each other, form a channel 57 with an essentially U-shaped cross-section intended, in an interaction that exerts control, to overlap partly with one of the existing outer longitudinal frame beams 58 of the vehicle, suggested by dot-dash contours (see Figures 2 and 6), before the parts are joined by welding. The support arms 27 and the components 30, 31 , of the spring facility that are parts of the separate suspensions 14 are therefore arranged at such a level under the longitudinal frame beams and in such a manner that the components of the suspensions are located in a plane A that is common for each suspension and that is oriented in the longitudinal direction of the vehicle (see Figure 5). The frame beams 22 constructed as extended pieces of sheet metal are provided with holes 59 intended to serve as attachment points for air bellows 31 and shock absorbers 30.

Each one of the suspension plates 50 is provided at its bottom with a rigid, relatively short, beam construction 60 that extends backwards in the longitudinal direction of the vehicle 1 and which beam construction is terminated with a backwardly facing gable 62 that is set transverse to the longitudinal direction of the vehicle and provided with the above- mentioned joints 29, for the formation of a first and second part, respectively, for the connection of the front end 28 of the support arm 27. The joint 29 is constituted by a forked joint in which the forward end 28 of the support arm 27 is inserted whereby, as is made clear by Figures 4, 5 and 6, the relevant support arm 27 is located directly under the longitudinal frame beam 22 in the common vertical plane A. As is made most clear by Figure 6, a part of the longitudinal frame beam 22 extends diagonally across the outer surface of the suspension plate 50 between an upper part and a lower part of the suspension plate, such that this part of the frame beam is located below the indentation 52.

The invention is not limited to what has been described above and shown in the drawings: it can be changed and modified in several different ways within the scope of the innovative concept defined by the attached patent claims.