GB2322604A

GB2322604A - Low floor bus chassis

Info

Publication number: GB2322604A
Application number: GB9801067A
Authority: GB
Inventors: Robert Erskin
Original assignee: Robert Wright & Son Coachworks
Current assignee: Robert Wright & Son Coachworks
Priority date: 1997-01-17
Filing date: 1998-01-19
Publication date: 1998-09-02
Anticipated expiration: 2018-01-19
Also published as: GB9700931D0; GB9801067D0; GB2322604B

Abstract

A low floor bus has a reinforced chassis comprising a front section (42) carrying front wheels and a rear section (46) carrying the rear wheels. The chassis also has a mid-section (40) extending between the front wheels and the rear wheels and connecting the front section and the rear section. The rear section is at a higher level than the front and mid-sections. In Fig 7A, a floor (20) is supported above the chassis on a sloping reinforcing frame (50) lying above the horizontal chassis mid-section (40), the reinforcing frame connecting the front section of the chassis (42) adjacent the front wheels with the rear section (46) of the chassis adjacent the rear wheels. Alternatively in Fig 8, the mid-section of the chassis comprises a single central beam 200 increasing in height from front to rear of the bus, to reinforce the chassis.

Description

LOW FLOOR BUS The present invention relates to low floor buses. Without detracting from the generality of that statement, the invention is particularly applicable to full size heavy duty PSV buses with rear engines as well as van-derived "mini" and "midi" buses which may, in addition, have front engines and/or be electrically powered.

Legislation outlawing discrimination against disabled people means that there is an increasing requirement for bus operators to provide buses that are readily accessible to the disabled and in particular that are capable of taking wheelchairs. These type of buses are known as "low floor" buses. Such buses have an entry step of less than 400mm between the road surface and the doorway to a useable passenger compartment. Under the relevant UK Code of Practice, the step height of a low floor bus should be 320mm at a maximum, and when account is taken of the height of a pavement this means that there is only a step of 70 to 90mm for a passenger to be able to get onto the bus. Such buses can be readily accessible by wheelchairs by placing a ramp from the doorway to the pavement, such ramps being accommodated within or beneath the buses.

Low floor buses have an inherently weaker chassis due to reduced chassis section depth.

Various proposals have been put forward to overcome this problem, namely, for example, the use of bonded windows to provide structural reinforcement to the bus body and hence additional support to the passenger compartment, and the addition of reinforcing plates to the side walls of the bus body for the same purpose. However, both of these proposals add very considerably to the cost of maintenance of the overall bus by comparison with the use of standard gasket glazing for the windows on a normal bus body.

According to a first aspect of the present invention there is provided a low floor bus having a chassis comprising a front section carrying front wheels and a rear section carrying the rear wheels, the said chassis also having a mid-section between the front wheels and the rear wheels and connecting the front section and the rear section, and a floor supported on the mid-section above the chassis, wherein the upper surface of the mid-section and the floor supported thereon slopes upwardly from the front to the rear of the bus.

According to a second aspect of the present invention there is provided a low floor bus having a chassis including a chassis frame carrying front wheels and rear wheels, the said chassis frame having a generally horizontal mid-section between the front wheels and the rear wheels, a floor supported above the chassis, and a reinforcing frame connecting a front section of the chassis adjacent the front wheels with a rear section of the chassis frame adjacent the rear wheels and in which the rear section of the chassis frame is raised above the front and the mid-sections, and the reinforcing frame provides a gradual slope from the front section to the rear section and supports part of the floor such that the floor has a corresponding slope.

The reinforcing structure adds significantly to the structural integrity of the chassis and obviates the need for additional structural reinforcing of the bus body and passenger compartment.

Advantageously, the reinforcing structure overhangs both the front section of the chassis and the rear section of the chassis providing the necessary structural strength between the front chassis and mid-section and between the rear chassis and mid-section.

An embodiment of the invention described below features a reinforcing structure comprising a frame having parallel longitudinal bars with transverse and diagonal connecting struts; alternatively, the mid-section chassis frame and the reinforcing frame can together form a single beam.

Further, a low floor bus embodying the invention can conveniently employ gasket glazed windows.

The invention is described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view, with parts broken away, of a bus embodying the present invention; Figure 2 is a side view of the bus partly in section and showing the chassis and a reinforcing frame; Figures 3 to 7 represent the steps involved in producing the chassis and reinforcing structure according to the present invention, with Figures 3a to 7a being side views of the chassis and reinforcing frame and Figures 3b to 7b being plan views of the same; and Figures 8 and 9 represent a second embodiment of a bus according to the present invention; Figure 8 is a perspective view of part of the chassis mid-section of such a bus and Figures 9a and 9b are plan and side views of the chassis and reinforcing structure of that bus.

Referring initially to Figures 1 and 2, a low floor bus comprises a chassis 10 (see Figure 2) carrying front wheels 12 and rear wheels 14 and supporting a bus body 16 providing a passenger compartment 18. The bus body 16 includes a sloping floor 20, side walls 22 and a roof 24. Seats 26 are mounted on the sloping floor 20 as shown, and the side walls 22 include standard gasket glazed windows 28 and doors 30.

The bus is a low floor bus as described above.

The chassis 10 includes a chassis frame 40 described in greater detail below and having a horizontal front section 42, a mid-section 44 and a raised, sloping rear section 46. These can be seen in greater detail in Figure 7a. The front section 42 extends forwardly from the front wheels 12, the mid-section 44 extends rearwardly from the front wheels 12 to a position a short distance in front of the rear wheels 14, and the rear section 46 extends from this position rearwardly to the rear wheels 14 and then rearwardly of the rear wheels 14. The mid-section 44 includes a horizontal frame 43 and an additional reinforcing frame 50 mounted to overlie the horizontal frame 43 and connecting the front section 42 to the rear section 46. The reinforcing frame 50 is joined to the front section 42 at a point 52 immediately in front of the front wheels 12 and is connected to the rear section 46 at a location 54 a little way in front of the rear wheels 14. Reinforcing straps 109 (see Figure 6a) complete the interface. Hence, the reinforcing frame 50 overhangs the horizontal frame and overlies a part of both the front section 42 and the rear section 46.

As shown in Figure 7a, the reinforcing frame 50 slopes from the front section 42 gradually upwardly towards the rear section 46 and provides a structurally rigid support for the bus body 16, and in particular for its sloping floor 20 which lies along the reinforcing frame 50.

Further details of the construction of both the chassis 10 and the reinforcing frame 50 will be apparent from the following description of Figures 3 to 7 and the steps involved in the production of the chassis 10.

Referring now to Figures 3a and 3b, a standard bus chassis is separated into a front section 62 and a rear section 64. The front section 62 includes the front wheels 12, a rigid horizontal frame 66 extending from the front 68 of the chassis to a point just behind the front wheels 12, a steering wheel 70 and a dash panel 72; this front section becomes the front section 42 of the low-floor bus chassis described above. The rear section 64 includes the rear wheels 14 and a stepped rigid support 74 having a lower bar 76 forwardly of the rear wheels 14, a gradually sloping upper step 78 rearwardly of the wheels 14 and an angled connecting bar 80 joining the bar 76 and the step 78; this rear section becomes the rear section 46 of the low-floor bus chassis. The motor 82 (shown schernatically) is also located at the rear section 64 and can be a conventional diesel engine or an electric motor.

As shown in Figure 3b, both front and rear sections 62, 64 comprise parallel bars 84, 86 joined by transverse connecting struts 88.

Turning to Figures 4a and 4b, the front and rear sections 62, 64 are converted into the front and rear sections 42, 46 of the bus chassis frame by the addition of mid-section 44 between them. More especially, as shown in Figure 4b, the mid-section 44 comprises the horizontal frame having two rigid parallel bars 90 joined by perpendicular cross struts 92 and diagonal cross struts 94 and a pair of converging struts 96 at the front. The top and bottom faces of the horizontal frame 43 are rigidly welded by means of small plates 98 to the top and bottom faces of the front and rear sections 42, 46.

The chassis frame (including the horizontal frame 43) as shown in Figures 4a and 4b is of generally conventional design and is relatively flexible; it includes areas of weakness in the regions of the joins. Such a chassis would have insufficient strength or stiffness without reinforcement for use on a full size heavyweight bus and would also be excessively flexible for use in midi or mini size buses under circumstances of heavy wear.

According to the present invention, the reinforcing frame 50 is added as shown in Figures 5 to 7.

Turning now to Figure 5a, a pair of sloping or quadrilateral rear plates 100 is added to the rear section 46 between the lower bar 76 and the angled connection bars 80. The rear plates 100 are welded at their rear ends to the rear section 46 and at their front ends to the horizontal frame 43. As can be seen in Figure 5b, the rear plates 100 extend forwardly and parallel to one another towards the mid-section 44.

Figures 6a and 6b show the addition of a further portion of the reinforcing frame 50, comprising a framework 102. The framework 102 comprises a pair of rigid longitudinal bars 104 extending parallel to one another. As in the case of the mid-section 44, the bars 104 are joined by perpendicular struts 106 and diagonal struts 108. However, the arrangement of the framework 102 relative to the mid-section 44 is such that the bars 104 are positioned inside the bars 90 and the perpendicular struts 106 do not overlie the perpendicular struts 92 nor do the diagonal struts 108 overlie the diagonal struts 94.

Furthermore, the front ends 110 of the longitudinal bars 104 extend forwardly of the horizontal frame 43 to the front of the front wheels 12 and hence overlie the front section 42. Likewise, the rear end 112 of the longitudinal bars 104 extend rearwardly beyond the mid-section 44 to just in front of the rear wheels 14 and hence overlie the rear section 46.

The front ends 110 of the longitudinal bars 104 are welded down onto the top surface of the front section 42, and the rear ends 112 of the longitudinal bars 102 are welded sideways onto the rear brackets 100. Furthermore, as shown in Figure 6a, the reinforcing frame 50 slopes gradually downwardly as it extends forwardly from the rear section 46 to the front section 42. Reinforcing straps 109 are welded to the framework and to the chassis rear frame 46.

Figures 7a and 7b show the completed chassis frame 40 (including the reinforcing frame 50) with the sloping bus floor 20 added on top. As can be seen, the gradient of the bus floor 20 follows the gradient of the reinforcing frame 50, i.e. the longitudinal bars 104, and the rear section 46 with a shallow step 120 between the two sections of gradient.

The combined chassis frame 40 and reinforcing frame 50 provide a rigid understructure to the remainder of the bus, having sufficient strength to be used even on full size heavyweight buses. The rigidity of this understructure reduces the stress levels on the bus body 16 very considerably such that additional reinforcing is unnecessary. As a consequence, the windows 18 of the bus are not required to provide structural reinforcement and standard gasket glazed windows can be used without disadvantage; nor are stress panels required.

The described embodiment minimises the minimum number of steps (if any required at all) in the passenger compartment by virtue of the slope in the reinforcing frame 50 and the sloping floor 20, which is a safety enhancing feature.

A bus according to the present invention is likely to meet DPTAC recommendations and forthcoming UK regulations.

Various modifications are possible in the described arrangement and, for example, the precise design of the reinforcing frame 50 constituting the longitudinal bars 104, perpendicular struts 106 and diagonal struts 108 can be substituted by an alternative arrangement of structural elements. Also, as shown in Figures 8 and 9, the mid-section 40 of the chassis, instead of being a separate horizontal frame and a reinforcing frame, can be combined to form a single central backbone frame in the form of a single beam 200 of top hat" cross section and including flanges 201. The beam increases in thickness from the front of the bus to the rear and so has a generally horizontal lower surface and a sloped upper surface.

Parallel arms 202 extend transversely away from the beam 200 and also are of 4 top hat" cross section and also include flanges 204. The space between the arms 202 form compartments 206 for accommodating the batteries of an electrically powered bus. Such batteries can be held on pallet trays of a size comparable to the size of the compartments so that the edges of the trays rest on and are carried by the flanges 201 and 204 of the beam 200 and the arms 202. In addition to providing accommodation for the batteries, the arrangement of Figures 8 and 9 provide ready access to them since spent batteries are readily removed from a bus in the illustrated embodiment by lifting the pallet trays out from each compartment (usually by means of a fork lift truck) and recharged batteries can readily be inserted in their place. An angle piece 208 can be secured to the ends of the arms 202 of each compartment to prevent the pallet trays sliding out from their respective compartments while the bus is in use. The arms 202 also support part of the bus superstructure (not shown).

The gasket glazed windows 18 of the bus may be replaced by bonded glazed windows according to customer preference.

The preferred embodiments of this invention thus provide a light weight and lower cost way of manufacturing a structurally sound, easily and economically maitainable and repairable low-floor bus body by using a chassis reinforcement structure (largely protected by its location from accidental traffic damage), permitting the use of gasket glazing to replace bonded glazing and/or body stress panels, both of which are relatively high-risk accident zone areas.

Claims

1. A low floor bus having a chassis comprising a front section carrying front wheels and a rear section carrying the rear wheels, the said chassis also having a mid-section between the front wheels and the rear wheels and connecting the front section and the rear section, and a floor supported on the mid-section above the chassis, wherein the upper surface of the mid-section and the floor supported thereon slope upwardly from the front to the rear of the bus.

2. A low floor bus having a chassis including a chassis frame carrying front wheels and rear wheels, the said chassis frame having a generally horizontal mid-section between the front wheels and the rear wheels, a floor supported above the chassis, and a reinforcing frame connecting a front section of the chassis adjacent the front wheels with a rear section of the chassis frame adjacent the rear wheels and in which the rear section of the chassis frame is raised above the front and the mid-sections, and the reinforcing frame provides a gradual slope from the front section to the rear section and supports part of the floor such that the floor has a corresponding slope.

3. A bus according to claim 1 in which the mid-section comprises a generally horizontal section and a reinforcing frame lying at least partly above the horizontal section.

4. A bus according to claim 2 or 3 in which the reinforcing frame overlaps the front section of the chassis.

5. A bus according to any of claims 2 to 4 in which the reinforcing frame overlaps the rear section of the chassis.

6. A bus according to any one of claims 2 to 5, in which the reinforcing frame comprises parallel longitudinal side bars having generally transverse connecting struts.

7. A bus according to claim 6 in which the reinforcing frame further comprises plates connected to the rear ends of the parallel longitudinal bars and raising the rear ends above the front ends of the parallel longitudinal bars.

8. A bus according to claim 1, in which the chassis mid-section comprises a single beam having a sloping upper surface and a lower surface that is generally horizontal.

9. A bus according to any one of claims 2 to 7, in which the chassis mid-section and the reinforcing frame together comprise a single frame having a sloping upper surface and a lower surface that is generally horizontal.

10. A bus as claimed in claim 9, in which the single frame is a beam.

11. A bus as claimed in claim 8 or claim 10 which includes generally transverse arms extending from the beam and defining with the beam compartments for accommodating batteries to power the bus.

12. A bus according to claim 11 in which the beam and the arms extending therefrom include generally horizontal flanges for supporting batteries or battery carriers in the said compartments.

13. A bus according to any preceding claim wherein the floor includes a single step having a height not exceeding 30 cm.

14. A bus according to any preceding claim wherein the front section of the chassis comprises a distinct structural chassis frame carrying the front wheels and the rear section of the chassis comprises a distinct rear chassis frame carrying the rear wheels, the front and rear chassis frames being connected together by the said chassis mid section.