The present invention relates to a chassis frame of the kind indicated in the preamble of claim 1. A chassis frame for a motor vehicle, such as a light or heavy truck, constitutes a loadbearing structure on which such items as the vehicle's engine, power transmission and wheel suspension are mounted. Other vehicle components such as fuel tank, compressed air reservoir etc. may also be mounted on the vehicle's chassis frame.

State of the art A chassis frame of the abovementioned kind generally comprises a pair of mutually parallel frame side-members which extend in the longitudinal direction of the frame and are joined together by some kind of transverse connecting elements such as frame cross-members. Frame side-members are usually U-shaped or C-shaped elements made of high-strength steel, while the cross-members may be made of pressed sheet steel. The cross-members may be fastened to the frame side-members by means of riveted, screwed or welded connections.

A disadvantage of such conventional chassis frames is their relatively great weight which entails, for a certain maximum total vehicle weight, a limitation of the vehicle's load capacity, i. e. the vehicle's ability to carry payload.

Objects of the invention The primary object of the invention is to provide a new type of chassis frame which is particularly suitable for special heavy trucks with fixed basic structure and which is of lower weight than corresponding previously known chassis frames of conventional types. To prevent the lower weight entailing any impairment of the chassis frame's rigidity, the provision of a frame structure which exhibits high torsional rigidity/flexural rigidity is also an essential object of the invention.

A further object of the invention is to provide a chassis frame which together with an associated basic floor results in a well-defined force distribution in the chassis.

Yet another object is that the chassis frame should be well-suited for mounting such vehicle components as fuel tank, compressed air reservoir, exhaust silencers, battery box, side underrun protection etc.

Summary of the invention The abovementioned objects are achieved according to the invention by the chassis frame indicated in the introduction exhibiting the features indicated in the characterising part of claim 1. The result is a light chassis frame with integrated load carrier.

A primary characteristic of the chassis frame according to the invention is that each frame side-member is a rolled section (preferably with U-shaped or C-shaped cross- section) made of sheetmetal. The two frame side-members are fitted with their respective webs situated in mutually parallel vertical planes, and with their flanges situated in mutually parallel horizontal planes, so that the upper and lower flanges respectively of each member are in the same planes as the corresponding flanges of the other member. A horizontal basic floor is fitted directly on top of the upper flanges of the frame side-members. Bracket-like outriggers which provide support for the portions or areas of the basic floor which are situated laterally beyond the webs of the frame side-members are fitted to the frame side-member web outsides, which face away from one another. Transverse elements which may take the form of substantially planar bulkheads or of transverse members are fitted between, and connect together, the respective webs of the frame side-members.

The chassis frame according to the invention may also exhibit the further-developing features indicated in the dependent claims.

The basic floor may for example comprise corrugated metal sheeting or be composed of rolled metal section elements. The metal thickness of the rolled section members is preferably less than 5 mm, while the transverse connecting elements are preferably made of sheetmetal not more than 3 mm thick. At least centrally to each transverse connecting element in the form of a thin sheetmetal bulkhead between the frame side- members, it is advantageous to fasten to the outside of the respective frame side- member web an outrigger which may be in the form of a right-angled triangle, in which case it has its shorter cathetus side fastened to the outside of the web of the adjacent frame side-member and its longer cathetus side provides support for the underside of the basic floor.

It is also possible to fit a suitable number of triangular outriggers in a reverse position, i. e. with the longer cathetus side situated parallel with and at a distance below the underside of the basic floor. The"triangular tips"of the outriggers will then be situated at said distance directly below the outer edges of the basic floor, where the outrigger tips may be used as supporting and suspension points for, for example, vertically arranged side underrun protection situated in the area below the outer edge of the basic floor.

The basic floor constitutes with advantage part of a load platform which is mounted directly on the upper flanges of the frame side-members so that the floor forms a force- absorbing structural element which actively contributes to the rigidity of the chassis frame.

In cases where corrugated metal sheeting is used as a structural element in the load platform, it is in practice necessary to fit an impact and shock resistant planar wearing layer on the top of this corrugated sheeting. This wearing layer may comprise sheetmetal (preferably aluminium) or plywood. A load platform of such design properly fastened (anchored) to the frame side-members will act as a force-distributing structural element whose flexural rigidity makes an active contribution to the total flexural rigidity of the chassis frame.

Not only the bulkheads and outriggers but also the basic floor may preferably be made partly or wholly of corrugated metal sheeting less than 3 mm thick.

A chassis frame according to the invention makes it possible to achieve a rigid chassis structure of lower weight than corresponding previously known structures. The components of the chassis frame can be both modularised and standardised, meaning respectively that they are suitable for a multiplicity of different applications and need only be made in a small number of variants. The new type of chassis frame according to the invention results in a well-defined force distribution in the chassis, and the fact that the basic floor/load platform constitutes an integrated part of the overall chassis structure makes the latter's torsional and flexural rigidity considerably greater than could otherwise have been achieved, as well as making it easier to mount any possible superstructure on the floor/platform.

Brief description of the drawings The invention is described and explained further below with reference to some highly schematic drawings depicting a truck provided with a chassis frame according to the present patent application.

The drawings are as follows: Fig. 1 depicts very schematically the truck in perspective as seen obliquely from above and behind; Fig. 2 depicts the truck according to Fig. 1 as seen directly from the side; Fig. 3 depicts the truck according to Fig. 1 as seen obliquely from beneath and behind; Fig. 4 depicts an example of the truck, as seen directly from behind, when provided with a boxlike superstructure mounted on the chassis frame's basic floor; Fig. 5 depicts on the larger scale the rearmost area of the load platform of the truck according to Fig. 3;

Fig. 6 depicts the truck according to Fig. 3 when provided with side underrun protection; and Fig. 7 depicts finally, on a somewhat smaller scale, the truck according to Fig. 6 as seen obliquely from above and in front.

Description of embodiments depicted in the drawings The truck depicted in Figs. 1-3, which is a cab-over-engine two-axled truck designated generally by ref. 10, has a chassis frame 12 comprising two parallel frame side- members 14,16 which are connected together in the frame's transverse direction by a number of transverse connecting elements. These transverse connecting elements, which are fastened by bolting, riveting or welding between the respective webs 14a, 16a of the frame side-members 14,16, take the form of bulkheads or transverse members 18 with lightening (weight reducing) holes 18a, 18b, 18c (see Figs. 4-5).

These bulkheads are preferably made of sheetmetal less than 3 mm thick.

As most clearly illustrated in Figs. 4 to 6, the frame side-members 14,16 are rolled metal sections with vertical webs 14a and 16a respectively and upper and lower flanges 14b, 14c and 16b, 16c respectively. In the case depicted, each frame side- member (14 and 16 respectively) has its flanges pointing inwards towards the flanges of the other member, but it is of course also perfectly possible to arrange the respective members with their flanges pointing outwards, i. e. with the flanges of one member directed away from the flanges of the other member.

The webs 14a, 16a are provided with large lightening holes 20. The metal thickness of these members is less than 5 mm. A horizontal basic floor 22 is mounted on the upper flanges 14b, 16b of the frame side-members 14,16. The frame side-members are also dimensioned with the webs 14a, 16a tall enough to allow the basic floor 22 to be mounted directly on top of the flanges 14b, 16b and yet leave sufficient space for the truck's rear wheels 24 and their springing movement upwards towards the basic floor 22.

As most clearly depicted in Fig. 3, bracket-like triangular outriggers 26 made of sheetmetal which is not more than 3 mm thick are mounted on the outsides of the webs 14a, 16a of the frame side-members 14,16 at a multiplicity of points along the chassis frame (ten points in Fig. 3). These outriggers 26 are positioned in pairs, on opposite sides of the frame side-members 14,16, centrally to one another in vertical planes perpendicular to the longitudinal direction of the chassis frame. The outriggers 26 provides support for the outer sections of the basic floor 22 which are situated laterally beyond the frame side-members 14,16. Particularly suitable points for pairs of outriggers 26 are central relative to each sheetmetal bulkhead 18. In addition to supporting outer sections of the basic floor 22 from beneath, the outriggers 26 may also be used as supports for various kinds of chassis-mounted vehicle components, e. g. fuel tank, battery box, compressed air reservoir, exhaust silencer and side underrun protection 28 (see Figs. 6 and 7).

The bulkheads 18 may also be designed to perform two or more functions, such as supports for various kinds of components. They may also be fitted separately as cross- members between the frame side-members 14,16, in order to distribute large forces from one frame side-member to the other. Such forces may for example derive from spare wheel carriers, axle fastenings, shock absorbers etc.

In the case of the truck 10 depicted in the drawings, the basic floor 22 forms part of a load platform mounted rigidly on the upper flanges 14b, 16b of the frame side- members 14,16, so that the floor forms a structural element which actively contributes to the torsional and flexural rigidity of the chassis. The basic floor may be made of corrugated metal sheeting 34 (see Fig. 1, Fig. 5 and Fig. 7) or be composed of rolled metal sections.

For practical reasons, the top of the corrugated metal sheeting is covered with a special wearing layer 30, e. g. of sheetmetal or plywood. The corrugated metal sheeting of the basic floor may be fitted so that the corrugations run either transversely to or parallel with the longitudinal extent of the frame side-members.

The so-called edgeline, i. e. the outer profile of the basic floor (ref. 32 in Fig. 1) may of course in practice be adapted to the particular type of basic structure, e. g. platform/box, sideflaps etc.