GB2303297A - Improvements in or relating to vehicle seat frames - Google Patents

Description

IMPROVEMENTS IN OR RELATING TO VEHICLE SEATS This invention relates to improvements in or relating to vehicle seats. In particular, the invention relates to a framework for a vehicle seat; a vehicle seat incorporating such a framework; and a vehicle incorporating such a framework or seat.

In recent years there has been much public debate about the safety of seating in road vehicles, such as minibuses and coaches, intended to carry passengers. An area of particular concern has been the safety of seating in minibuses used by schools for transporting pupils e.g. to and from events distant from school premises; or even in school grounds.

Following a number of widely publicised, serious road accidents involving minibuses and coaches, there has been growing public pressure for legislation to improve the safety of seating for passengers in such vehicles.

EC Directive 76/11 5/EEC relates to the testing of passenger seat belts in new vehicles. However, there is presently no regulatory safety test relating to the seat and seat belt installations in pre-existing vehicles.

The nature of the test specified in Directive 76/115/EEC is such that the composite assembly of vehicle, seat and seat belt is tested in a single test (known as a "pull test") in which a rigid member such as a piece of wood is pulled against the tension in a seat belt secured to a seat itself secured in a vehicle. Thus, a seat and seat belt combination can only pass the test in the directive when installed in a vehicle, and there is no generic test that enables the safety certification of a seat and seat belt combination for all possible vehicles into which the combination could be installed.

It has been found during the testing of passenger seat and seat belt combinations in vehicles such as minibuses that the floors of minibuses are commonly not sufficiently strong to provide an adequate anchorage during the pull test.

Consequently, although a vehicle seat may itself be structurally strong the combination of such a seat with a vehicle may fail the pull test in Directive 76/115/EEC because the floor of the vehicle tears or buckles unacceptably.

Patent Application No. GB 9414872.3 filed on 23 July 1994 relates to a strengthening framework that may be installed above a mini bus floor to provide a strong mounting for passenger seats thus enabling the vehicle, seat and seat belt combination to pass the pull test specified in the directive referred to.

A typical passenger seat intended for installation in minibuses is of a design such as that shown in Figure 1.

In Figure 1 there is shown a prior art seat 10 comprising a tubular framework 11 defining a seat base portion 11 a and a backrest portion 11 b. Seat base portion 11 a is bolted via spacers 12 onto a leg assembly 13. The feet 13a, 13b of leg assembly 13 are bolted to e.g. the floor of the vehicle in which the seat 10 is installed.

Padded upholstery 14 is applied to the seat for the comfort of users thereof; and in the prior art embodiment shown there is a head restraint 15.

Commonly, the belt dispensing drum of e.g. an inertia reel, diagonaailap type seat belt is bolted through the upholstery to the rear of backrest portion 11 b of framework 11, e.g. in the position indicated by arrow D. The chest strap part of the seat belt webbing then passes over the top 1 4a of the upholstered portion of the back of seat 10, to be available above the shoulder of a user of the seat.

Although the seat 10 of Figure 1 appears to include numerous safety features such as a diagonal/lap-type seat belt, a head restraint 15 and a heavily engineered leg assembly 13, in fact seats such as seat 10 tend to fail the pull test of Directive 76/115/EEC when used in vehicles fitted with a floor strengthener of the kind described in Patent Application No. GB 9414872.3. This problem arises principally because the strengthening arrangement of the aforementioned patent application is structurally stronger than a seat such as seat 10, and therefore when the pull test is carried out the weaknesses of the seat 10 are exposed. Typical failures of seat 10 include catastrophic bending of the framework 11 at the point 1 it; tearing or buckling of the leg assembly at the points 13c, 13d; and twisting of the seat portion 1 la.These problems went unnoticed in the past, since unstrengthened mini bus floors tended to fail much more readily than the seats 10, thereby masking the problems inherent in the seats 10.

Some vehicle seat manufacturers have resorted to modifying their seats in a manner specific to their installations in particular vehicles, in order that the vehicle/seat combination will pass the pull test in the EU Directive referred to above.

However, this approach, which usually involves welding additional strengthening pieces to the seat legs and framework, is not only very expensive to achieve; there are also dangers associated with inconsistent work quality from one seat to the next, or even of a wrongly modified seat being installed in a particular vehicle. EC Directive 76/115/EC includes specific provisions relating to conformity of production.

Clearly there is a risk that the directive will not be complied with if the vehicle seats are modified in a manner specific to their installations in particular vehicles.

Furthermore, the modification of seats by welding of strengthening pieces to their frameworks increases the weight of each seat and hence of a vehicle incorporating such seats. This is undesirable partly because vehicle performance characteristics may thereby be affected; and more importantly because the gross vehicle mass may be increased to such an extent that the vehicle has to be re-classified as to its safety characteristics.

Thus there is a strong need for a light weight, low-cost, high strength, batchor mass-producible passenger seat for vehicles such as minibuses and coaches the floors of which have been strengthened sufficiently to pass the full test specified in the Directive 76/115/EEC.

According to a first aspect of the invention, there is provided a framework for a vehicle seat, the framework comprising a plurality of rigidly interconnected members defining a seat portion and a backrest portion of the framework, wherein: (i) the seat portion includes a transversely extending member and a rearwardly extending member, the transversely extending member including an aperture that receives the rearwardly extending member; and/or (ii) the seat portion includes at least one seat bracing member rigidly interconnecting the transversely extending member and the rearwardly extending member or one or more further members connected thereto; and/or (iii) the back portion includes a member extending upwardly relative to the seat portion, and at least one back bracing member rigidly interconnecting the back portion and the seat portion.

Each of the features labelled (i)-(ii) above confers advantageously high strength on the framework when used alone; furthermore, it has been found that unexpected benefits in terms of framework strength arise when two or more of the numbered features are used in combination in a framework.

Preferably, the seat includes a pair of mutually spaced, rearwardly extending members and a corresponding pair of apertures in the transversely extending member for receiving the respective rearwardly extending members. The use of a pair of rearwardly extending members allows for the ready manufacture of a structurally strong, symmetrical stable seat.

It is also preferable when the seat includes a pair of mutually spaced, rearwardly extending members for the framework to include a corresponding pair of seat bracing members.

Conveniently the framework includes a pair of mutually spaced members extending upwardly relative to the seat portion. The use of a pair of such members again confers symmetry and strength on the structure. If a pair of upwardly extending members is employed, it is convenient to use a corresponding pair of back bracing members.

In preferred embodiments, the transversely extending member is hollow and open at least at one end, the or a said seat bracing member including a surface secured to and substantially closing said open ends.

The use of a hollow member confers lightness on the framework, and the closing of the end of such a member by virtue of a surface forming part of the seat bracing member improves its torsional strength.

In particularly preferred embodiments, the transversely extending member is of generally rectangular cross-section. Such a cross-section is comparatively cheap to produce and the regularity of its shape permits the ready attachment of further members thereto.

In preferred embodiments, the or each back bracing member lies generally forwardly of the upwardly extending members. Thus, an upwardly extending member, its associated back bracing member and a portion of the seat portion of the framework lying between the back bracing member and the upwardly extending member between them define a triangle that is structurally very strong and resistant to forward bending of the back portion of the framework about the junction between the back portion and the seat portion.

Conveniently the seat portion is polygonal in plan view, and each seat bracing member interconnects the upper end of a respective upwardly extending member and a rear corner of the seat portion. This arrangement allows ready manufacture of the triangular arrangement of the members referred to above.

Preferably the framework includes a backrest support extending transversely of the back portion, the backrest support including a surface for receiving and supporting a laminar backrest. Preferably the backrest support extends between the respective back bracing members.

The arrangement advantageously allows the use of e.g. a fibre-board back rest that is readily secured (e.g. by means of rivets) into the framework. A laminar, fibreboard backrest can easily be adapted for the securing thereto of upholstery.

The framework may also optionally include a pair of guide surfaces secured respectively to the backrest support and defining a channel for receiving the laminar backrest. Such an arrangement constrains the laminar backrest when fitted against movement relative to the remainder of the seat; provides suitable points for the fastening of rivets securing the laminar backrest into the framework; and provides a pair of guide channels along which the edges of the laminar backrest may be slid during assembly of a seat, thereby assisting and speeding the manufacturing process.

The framework may optionally include a further, transversely extending member rigidly interconnecting the upwardly extending members adjacent their upper ends. Such a member confers rigidity on the upper part of the backrest portion, and allows the upper ends of the upwardly extending members to be shaped in order to define an integral head restraint that is stronger than prior art, separately attached head restraints.

Preferably there is included a belt guide member secured on the framework adjacent the further, transversely extending member. It is also preferable that the framework includes operatively secured thereto a diagonal/lap seat belt assembly, the belt drum of which is secured to the seat portion of the framework and the belt of which passes under the seat portion, up the back portion of the framework and over the further, transverse member via the belt guide member (if present). An advantage of this arrangement is believed to be that the position and mounting of the seat belt assembly can be chosen such that part of any impulse applied to the seat belt is absorbed by the further, transversely extending member.Thus, part of the load induced in a seat belt system secured in the framework according to the invention is borne by the framework itself and this part of the load is not borne by the attachment screws for the seat belt dispensing drum. This contrasts with the situation in prior art seats such as that shown in Figure 1, in which virtually all the loading on the upper part of the seat belt is borne by the drum and its attachment screws.

It is also preferable that the framework includes secured thereto a socket for the fastening buckle of the seat belt assembly. Consequently, the seat belt arrangement can be made integral with the seat thereby reducing the need for attachment points on the vehicle floor.

The invention is also considered to reside in a vehicle seat including a framework as defined hereinabove. Preferably, when the framework includes the further, transversely extending member referred to above, the vehicle seat includes an aperture in the upholstery of the backrest portion thereof corresponding to the position of the transversely extending member and permitting free passage therethrough of a seat belt.

Furthermore, the invention is considered to reside in a vehicle including a framework as defined hereinabove or a vehicle seat as defined hereinabove.

In addition, the invention is considered to reside in a framework generally as herein defined modified to provide multiple seating in a side by side arrangement.

For the avoidance of doubt, whilst the invention has been described in relation to its use in vehicles such as minibuses and coaches, the seat of the invention can be used in a great variety of other vehicles such as passenger cars, trains, hovercraft, jetfoils, airships, and other forms of aircraft including aeroplanes.

There now follows a description of a preferred embodiment of the invention, by way of example, with reference being made to the accompanying drawings in which: Figure 1 shows a prior art vehicle seat; Figure 2 is a front elevational view of a first embodiment of a framework for a vehicle seat according to the invention; Figures 3 and 4 are respectively a side elevational view and a plan view from above of the framework of Figure 2; Figure 5 shows a second embodiment of a framework according to the invention intended to provide multiple, side by side seating; and Figure 6 shows a leg sub-assembly suitable for use with the framework of Figures 2 to 5.

Referring to the drawings, there is shown in Figures 2 to 4 a framework 20 comprising a series of tubes and other members welded rigidly together to define a seat portion 21 and a backrest portion 22.

As is visible from Figure 4, seat portion 21 is polygonal, specifically rectangular, in plan view and includes as an important structural member a transversely extending member 23 at the front of the framework.

Extending rearwardly from transversely extending member 23 at either end thereof is a pair 24, 25 of rearwardly extending, tubular members which in the embodiment shown are of circular cross-section. The forwardmost ends 24a, 25a of the respective members 24 and 25 are received in circular, through-going apertures formed in the respective ends of transversely extending member 23. The ends 24a, 25a are secured rigidly by means of welds 24b, 25b.

Each rearwardly extending member 24, 25 extends generally horizontally and passes through respective through-going apertures formed in a second, transversely extending member 27. The apertures in through-going member 27 are aligned with their counterparts in through-going member 23 so that the rearwardly extending members 24, 25 are straight in the space between the transversely extending members 23 and 27.

To the rear of transversely extending member 27, the rearwardly extending members bend upwardly about a radius in the vicinity of reference numeral 28 visible in Figure 3. The respective members then straighten to define a pair of members 29, 30 extending inclinedly upwardly to define the outline of the backrest portion of the framework.

As is visible in Figure 3 the members 29, 30 are forwardly bent a short distance from their upper ends so that their uppermost portions extend substantially vertically. As is best seen from Figure 2, the upper ends of the members 29,30 are bent inwardly relative to the remainder of the backrest portion, and such bending of the members defines the outer edges of an integral head restraint portion 32 of the framework 20. Head restraint portion 32 is completed by generally horizontally extending member 33 interconnecting and, in the embodiment shown, integral with the respective, bent upper ends of the upwardly extending members 29, 30.

A pair 34, 35 of seat portion bracing members extend respectively along the left and right hand edges of the seat portion 21 as viewed in Figure 2. Each seat bracing member 34, 35 is a rectangular plate that is welded to an open end of transverse member 23, thereby closing the open end; and welded to predetermined points along the adjacent, rearwardly extending member 24, 25.

This arrangement permits the use of lightweight, hollow, rectangular section members as the members 23 and 27 since the addition of the seat bracing members 34, 35 provides torsional rigidity in the transversely extending member 23 and also provides resistance to bending stresses in the rearwardly extending members 24, 25 by virtue of attachment of the bracing members 34, 35 thereto.

Second, transversely extending member 27 is, similarly, a hollow, rectangular section member and the rigid securing of the seat bracing members 34, 35 thereto confers similar strength on this component.

The protrusion of the members 24, 25 through the members 23, 27 also improves their torsional strength and general resistance to bending stresses.

Securing of the seat bracing members 34, 35, and indeed the majority of the other components in the framework is by means of welding in the embodiments shown.

The framework also includes a pair 37, 38 of back bracing members. In the embodiment shown the back bracing members 37, 38 are oval section tubes that are welded in the framework in front of the upwardly extending members 29, 30.

Back bracing member 37 is welded at its upper end to upwardly extending member 29 adjacent the point at which member 29 is bent to extend vertically. The lowermost end of bracing member 37 is welded to the top of second, transversely extending member 27.

Back bracing member 38 is similarly secured on the right hand side of the framework as viewed in Figure 2.

It will thus be seen that the combination of the radiussed portion of the rearwardly extending members 24, 25; the upwardly extending members 29, 30; and the back bracing members 37, 38 define a pair of triangular frameworks at either side of the overall framework 20. Such an arrangement shows particular resistance to bending of the backrest portion of the framework.

Respective guide plates 40 are welded onto the rear edges of the back braces 37, 38 in order to define a channel extending longitudinally along the rear edge of each back bracing member 37, 38. The channels and the back rest support 39 between them define a shaped location for a laminar backrest (not shown in the drawings) that can be slid into place and secured e.g. by means of rivets at various points where it contacts the framework and/or further components secured thereto. The laminar backrest provides support for users of the seat and provides a suitable series of attachment points for upholstery. The backrest includes a through-going slot approximately at the height of the shoulder of a user of the seat. The slot is of use in the process of applying upholstery to the framework.

Referring again to Figure 2, there is shown a further, transversely extending member 42 that rigidly interconnects the upwardly extending members 29, 30 at the point at which they are bent upwardly and inwardly to define the head restraint portion 32 of the framework 20. This further, transversely extending member strengthens the upper portion of the framework, and in addition assists in the guiding of e.g. a webbing seat belt forming part of a seat belt assembly that may be secured in the framework during manufacture of a seat.

As is shown in Figure 2, a post 43 extends vertically from a position adjacent the left hand end of member 42 to the inwardly directed part of upwardly extending member 29 directly above the aforesaid point. In addition, a belt guide slot 44 is secured on a bracket that is welded to the framework so that guide slot 44 (which is formed as a rectangular aperture in a flat plate) is spaced forwardly of further, transversely extending member 42.

Thus, a seat belt may be passed from the underside of seat portion 21, up the outside of backrest portion 22, over the upper edge of further, transversely extending member 42 and through a suitable aperture or recess in the laminar backrest, (and, when present, the upholstery secured to the framework) to be presented at approximately the shoulder height of a user of the seat. The lap part of the belt can readily be secured at the left hand edge of the framework by means e.g. of a suitable weld nut or similar attachment (not shown); and a seat belt anchorage socket can be secured at the right hand edge of the framework as shown in Figure 1 by a similar means. Thus, the framework may be manufactured with an integral seat belt assembly that is safely guided by means of structurally strong guides such as member 42, post 43 and guide member 44, to an operational position.

The post 43 and guide slot 44, which latter is secured to the framework by means of rearwardly extending mounting side plates 44a interconnecting the guide slot 44 and the framework, may of course be provided at the right hand side of the framework as shown in chain lines in Figure 1. This is desirable because it is common practice for the anchorage socket for a seat belt in a vehicle seat of the kind described herein to be in a preferred position either adjacent to or remote from an aisle alongside the seat. The possibility of securing the components 43, 44 at either side of framework 20 permits the seat belt to be mounted on either side thereof.

In a further embodiment of the invention (not shown) the components 43, 44 may be provided on both sides of framework 20. This arrangement permits the construction of a so-called "welfare" seat, intended for use by passengers having poor control over their limbs, including an additional diagonal seat belt and an additional anchorage socket therefor so that such passengers may be restrained by a pair of belts crossing their upper bodies plus a lap belt.

It will be appreciated that some of the components 42, 43, 44 will, in the event of a sudden impulse applied to the seat belt webbing, bear some of the load induced thereby. Thus, the stresses induced at the mounting point for the seat belt drum are believed to be reduced compared with prior art vehicle seats in which the upper portions of the seat framework played very little part in absorbing stresses induced in the seat belt assembly.

Figure 5 shows a second embodiment of seat framework 120 in accordance with the invention. Framework 120 includes three seat portions and backrest pairs 20, each essentially similar to the embodiment of Figures 2 to 4, secured in a side by side relationship to provide multiple seating.

In the Figure 5 embodiment, the member 23 is shown as a member common to the three pairs 20 and extending across the entire width of the front of the framework. Member 27 (not visible in Figure 5) extends similarly, and the respective members 24 and 25 of the pairs 20 each pass through appropriately positioned apertures in the common members 23, 27. This arrangement provides multiple seating of great strength.

Of course embodiments similar to the Figure 5 embodiment may readily be constructed in accordance with the invention having more or fewer seat and backrest pairs 20 than the three shown if desired.

Furthermore the posts 42 and guide slots 44 may be variously positioned in the backrest portions of the Figure 5 embodiment (or any similar multiple seating arrangement) in a manner analagous to the equivalent components shown in Figure 2.

Thus multiple "welfare" seats may be constructed if desired.

Figure 6 shows a suitable leg assembly 46 for supporting the framework. One leg assembly is secured at each side of seat portion 21 by means e.g. of suitable shackle bolts securing the upper portions of the brackets 47 of the leg assemblies to the respective, transversely extending members 23, 27.

Each leg assembly 46 includes front 48 and rear 49, downwardly extending legs interconnected by a diagonal brace 50. This arrangement of leg assembly has been found to exhibit greater strength than the prior art leg assemblies such as that shown in Figure 1. The leg assembly shown in Figure 6 is of a generally known design that is of proven strength.

In multiple seating embodiments of the invention, such as the embodiment of Figure 5, two leg assemblies 46 are preferably used in a twin seating version; four leg assemblies 46 in a triple seat version; and so on.

The embodiments of seat framework shown in the drawings can be used as the base for a lightweight, highly safe vehicle seat. The material of the embodiment shown is mild steel, although a great variety of alternative materials, including but not limited to specialised alloys; certain plastics materials; and composite materials may equally well be used in specific applications of the design.

Claims (27)

1. A framework for a vehicle seat, the framework comprising a plurality of rigidly interconnected members defining a seat portion and a backrest portion of the framework, wherein: (i) the seat portion includes a first transversely extending member and a longitudinally extending member, the transversely extending member including an aperture that receives the longitudinally extending member; and/or (ii) the seat portion includes at least one seat bracing member rigidly interconnecting the or a first transversely extending member and the or a longitudinally extending member or one or more further members connected thereto; and/or (iii) the back portion includes a member extending upwardly relative to the seat portion, and at least one back bracing member rigidly interconnecting the back portion and the seat portion.

2. A framework according to Claim 1 including a pair of mutually spaced, longitudinally extending members and a corresponding pair of apertures in the first transversely extending member for receiving the respective longitudinally extending members.

3. A framework according to Claim 2 including a pair of seat bracing members rigidly interconnecting the respective ends of the first transversely extending member and the respective longitudinally extending members.

4. A framework according to any preceding claim wherein the seat portion includes a second, transversely extending member spaced from the first, transversely extending member.

5. A framework according to Claim 4 wherein the or a longitudinally extending member interconnects the first and second transversely extending members.

6. A framework according to any preceding claim including a pair of mutually spaced members extending upwardly relative to the seat portion.

7. A framework according to Claim 6 including a pair of back bracing members respectively rigidly interconnecting an upwardly extending member and the seat portion.

8. A framework according to any preceding claim wherein the transversely extending member is hollow and open at least one end, the or a said seat bracing member including a surface secured to and substantially closing said open end.

9. A framework according to any preceding claim, wherein the transversely extending member is of generally rectangular cross-section.

10. A framework according to any preceding claim wherein the or each back bracing member lies generally forwardly of the upwardly extending members.

11. A framework according to any preceding claim, wherein the seat portion is polygonal in plan view and each seat bracing member interconnects the upper end of a respective upwardly extending member and a rear comer of the seat portion.

12. A framework according to any preceding claim, including a backrest support extending transversely of the back portion, the backrest support including a surface for receiving and supporting a laminar backrest.

13. A framework according to Claim 12 when dependent from 7, wherein the backrest support extends between the respective back bracing members.

14. A framework according to any of Claims 11 to 13 including a pair of guide surfaces secured respectively to the backrest supports and defining a channel for receiving the laminar backrest.

15. A framework according to any of Claims 6 to 14 including a further, member extending transversely of the backrest portion and rigidly interconnecting the upwardly extending members adjacent their upper ends.

16. A framework according to Claim 15 including a belt guide member secured on the framework adjacent the said further member.

17. A framework according to Claim 15 or Claim 16 including operatively secured therein a diagonal/lap seat belt assembly, the belt drum of which is secured to the seat portion of the framework; and optionally a diagonal seat belt assembly and the belt of which passes under the seat portion, up the back portion of the framework and over the further, transverse member via the belt guide member (if present).

18. A framework according to Claim 17 including secured thereto a socket for the fastening buckle of the seat belt assembly.

19. A framework including a plurality of seat portions and a corresponding plurality of backrest portions arranged in a side-by-side relationship, at least one of said seat and backrest combinations including a framework according to any preceding claim.

20. A framework according to Claim 19 including a common first transversely extending member for the plurality of seat portions.

21. A framework according to Claim 19 or Claim 20 including a common second, transversely extending member for the plurality of seat portions.

22. A vehicle seat including a framework according to any preceding claim.

23. A vehicle seat including a framework according to Claim 22 when dependent from any of Claims 15 to 21, including an aperture in the upholstery of the backrest portion thereof, the aperture permitting free passage therethrough of the belt of a seat belt assembly.

24. A vehicle including a framework according to any of Claims 1 to 21 or a seat according to either of Claims 22 or 23.

25. A framework generally as herein described, with reference to or as illustrated in Figures 2 to 6 of the accompanying drawings.

26. A vehicle seat generally as herein described.

27. A vehicle generally as herein described.