GB2376411A

GB2376411A - Arrangement of low friction means in seat rail unit

Info

Publication number: GB2376411A
Application number: GB0114288A
Authority: GB
Inventors: Jan Franzen
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2001-06-12
Filing date: 2001-06-12
Publication date: 2002-12-18
Also published as: GB0114288D0

Abstract

Low friction means 21, 22, 23, 24 are located in a recess 12 between one rails 3 and a load plate 7 of the other rail 2. The rails 2, 3 have identical cross-section. At least one load plate 7 has a low friction means 21, 22 at each side. The low friction means 21, 22 on one side of the unit is higher than the low friction means 23, 24 on the other side. Preferably the low friction means 21, 22, 23, 24 are polytetrafluoroethylene balls.

Description

DESCRIPTION OF INVENTION "IMPROVEMENTS IN OR RELATING TO A SEAT RAIL UNIT" THE PRESENT INVENTION relates to a seat rail unit, and more particularly relates to a seat rail unit for a vehicle seat, so that the position of the vehicle seat may be adjusted axially relative to the vehicle in which the seat is mounted.

It is conventional to mount a vehicle seat in a motor vehicle by using a seat rail unit having a lower rail connected to the floor, and an upper rail connected to the seat. Sliding or rolling means, such as balls or rollers, are usually located operatively between these c-operating rails so that the upper rail may move freely relative to the lower rail. Conventionally locking and releasing means are provided so that the vehicle seat may be releasably secured at a selected position.

Many types of seat rail unit have been proposed previously.

DE-19717667 discloses an arrangement in which a lower rail is provided which has a specific rail profile, and an upper rail is provided which has a rail profile selected to co-operate with the rail profile of the lower rail in such a way that spaces are defined between flanges carried by the upper rail and

recesses defined by the lower rail to accommodate ball bearings or the like.

This arrangement does have the advantage that there is enough space provided with the interior of the combined rails for a drive mechanism for automatically adjusting the position of the seat or, alternatively, for a locking mechanism for a manually adjustable seat. The disclosed arrangement also has the advantage that the arrangement is not symmetrical about a vertical axis, with the flange associated with the balls on one side of the vertical axis being much higher than the flange associated with the balls on the other side of the vertical axis. This provides enhanced rigidity for the rail.

Nevertheless, the seat rail unit is relatively expensive to manufacture, and the present invention seeks to provide an improved seat rail unit which may be manufactured more economically.

According to one aspect of this invention there is provided a rail unit for a vehicle seat, the rail unit being constituted by two rails of identical crosssection which are inter-connected with each other, each rail having a load-plate received within a recess defined by the other rail, each load-plate being associated with at least one low friction means between the load-plate and the recess in which the load-plate is located, at least one load-plate being associated with two low friction means, there being one respective low friction means located on each side of that load-plate, the low friction means on one side of a notional vertical plane passing through the unit being at a higher level than the low friction means on the other side of the plane.

Preferably there are two low friction means associated with each loadplate.

Conveniently at least some of the low friction means comprise balls.

Preferably the balls are in the form of linear ball races.

Alternatively at least some of the low friction means comprise elongate elements having a low co-efficient of friction. Although there may be a mixture of balls and elongate elements as the low friction means.

Conveniently the elongate elements having a low co-efficient of friction are formed of a plastics material.

Preferably the plastics material comprises polytetrafluoroethylene.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a cross-sectional view of a seat rail unit in accordance with the invention, comprising two c-operating rail profiles, and FIGURE 2 is a corresponding view of a slightly modified embodiment of the invention.

In the illustrated embodiments of the invention a seat rail unit comprises two rails sections, but the rail sections have the same cross-section, meaning that it is only necessary to provide one die, or one set of forming rollers for forming the relevant section. This may serve to minimise manufacturing costs.

Referring initially to Figure 1 of the accompanying drawings, a seat rail unit I is illustrated which comprises a lower rail 2 and an upper rail 3.

The lower rail 2 and the upper rail 3 are each of the same cross-section.

Each rail is formed as an extrusion or as a metal rolling.

The lower rail 2 has a horizontal base section 4 which carries, at one side, an upstanding side wall 5. The upstanding side wall 5 terminates with an outwardly directed horizontal flange 6 which carries a downwardly and outwardly directed load-plate 7 which is of corrugated form.

The other side of the base section 4 of the lower rail 2 carries an upwardly inclined wall 8 which supports a vertically upstanding side wall 9 which carries an inwardly directed horizontal flange 10, which terminates with a vertical plate 11, which in the illustrated orientation is a depending plate. The sloping wall 8, the vertical wall 9, the horizontal wall 10 and the plate 11 together surround a space 12.

The upper rail 3 has the same cross-section as the lower rail as has been described. It can be seen that the two rails are brought together, with a relative axial movement, so that the corrugated load-plate 7 of each section is within the space 12 defined by the sloping wall 8 with a vertical wall 9, the horizontal flange 10 and the vertical plate 11 of the other rail.

Located on each side of the coll ugated load-plate 7 is one or more low friction elements 21, 22. The 10\\'friction element 21 is located above the corrugated load-plate 7, and the low faction element 22 is located below the corrugated load-plate 7. The low friction elements may comprise a plurality of

balls, such as a linear ball race or, alternatively, may comprise rods or other elongate elements formed of a plastics material having a low co-efficient friction, such as polytetrafluoroethylene.

In a corresponding manner, low friction elements 23 and 24 are provided between the load-plate of the upper rail 3, and the adjacent parts of the lower rail 2. Again the low friction elements may comprise balls or elongate elements of plastics material.

The provision of four low friction elements, with two low friction elements being provided in association with and on opposite sides of each load plate, provides for a smooth movement of the upper rail relative to the lower rail, with a minimum of distortion or"wobbling".

However, as shown in Figure 2, it is possible for one or more of the low friction elements to be omitted. In the embodiment shown in Figure 2, the lower low friction element 22 associated with the load-bearing plate 7 of the lower rail 2 has been omitted. The co-operation of the two low friction elements 23 and 24 with the load-bearing plate of the upper rail, will minimise any risk that the upper rail may move upwardly and downwardly in an undesirable manner, but there is still a slight risk that the upper rail section may tilt. Consequently, while it is preferred that each load-plate is associated with two low friction elements, one on each side thereof, one low friction element can be omitted. With the one low friction element omitted, the load bearing plate 7 has a higher degree of freedom of movement. Also the need for light tolerances is reduced, enabling less expensive manufacturing techniques to be used, and minimising stress within the rail unit. Thus a desired flexibility is provided.

It is to be observed that the seat rail unit described does have the advantage that the low friction elements at one side of a notional vertical plane 25 passing through the centre of the unit are at a higher level than the low friction elements on the other side of the vertical plane, thus enhancing the strength of the seat rail unit.

In the present Specification"comprises"means"includes or consists of and "comprising" means "including or consisting of'.

The features disclosed in the foregoing description, or the following Claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A rail unit for a vehicle seat, the rail unit being constituted by two rails of identical cross-section which are inter-connected with each other, each rail having a load-plate received within a recess defined by the other rail, each load-plate being associated with at least one low friction means between the load-plate and the recess in which the load-plate is located, at least one loadplate being associated with two low friction means, there being one respective low friction means located on each side of that load-plate, the low friction means on one side of a notional vertical plane passing through the unit being at a higher level than the low friction means on the other side of the plane.
2. A unit according to Claim 1 wherein there are two low friction means associated with each load-plate.
3. A unit according to Claim 1 or Claim 2 wherein at least some of the low friction means comprise balls.
4. A unit according to Claim 3 wherein the balls are in the form of linear ball races.
5. A unit according to any one of the preceding Claims wherein at least some of the low friction means comprise elongate elements having a low coefficient of friction.
6. A unit according to Claim 5 wherein the elongate elements having a low co-efficient of friction are formed of a plastics material.

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7. A unit according to Claim 6 wherein the plastics material comprises polytcirailuoroeihyiene.
8. A rail unit for a vehicle seat substantially as herein described with reference to and as shown in Figure 1 of the accompanying drawings.
9. A rail unit for a vehicle seat substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.
10. Any novel feature or combination of features disclosed herein.