The present invention relates to seat rails in a motor vehicle, and
more particularly to a method of manufacturing optimised seat rails.
Customarily a seat slide assembly in a vehicle comprises a first elongated
(bottom) rail fastened to the vehicle floor and a second elongated (top) rail mounted
on the first rail in a sliding and locking manner. The second rail is also applied
for fastening of seats and safety belts for occupants of the vehicle.
Due to a general tendency to reduce the vehicle weight rails extruded
in light metals, e.g. made of Al-alloys, have recently replaced rails made of steel.
A drawback of the applied extrusion manufacturing technique is that the provided
rails exhibit uniform cross-sections along their longitudinal extension (see for
example GB-A-1 061 680). Since the load imposed on the rails varies significantly
along their longitudinal extension, the rear part of the second (top) rail accommodating
fastening means (apertures) for the safety belts exhibits larger dimension than
the remaining front part of the rail. Currently applied solutions to achieve the
above configuration of the seat rails are either to provide a whole rail with sufficient
wall thickness and thus accidentally increase the weight or to remove the superfluous
material from the front part, something which necessitates an additional cutting
operation and material spill.
Another viable way to go is to reinforce the rear part of the rail
by attachment of external members, thus increasing the complexity and number of
components in the rail assembly.
Consequently, it is an object of the present invention to provide
a novel manufacturing method/principle resulting in an optimised design of seat
rails characterized by a unitary, light weight rail manufactured with minimum material
This and other objects of the present invention are achieved by provision
of a manufacturing method as claimed in the accompanying claim 1.
The invention will be described in details with reference to the attached
drawings, Figs. 1-3, where
- Figs. 1a,b,c,d
- show in a vertical cross-sectional view a different configuration of an intermediate
extruded shape usable for manufacturing of rails according to the invention,
- Fig. 2
- illustrates schematically the cutting step resulting in provision of two identical
- Fig. 3
- shows in a partial perspective view the seat rail applied as the top rail in
a seat rail assembly.
Referring to Fig. 1a two co-extruded rails (1,2) of identical cross-sectional
configuration covering the requested sliding and fastening functions are interconnected
along a reinforcing rib 3 laterally protruding from the side of the vertical rail
wall 4. This unitary shape extruded in Al-alloy in one simple operation provides
an intermediate product for the following single cutting operation as illustrated
in Fig. 2 by the resulting separated rails 1,2. By alternately moving the cutting
tool (not shown in the Figure) back and forth (up and down), thus following the
upper side and the bottom side of the reinforcing rib 3, two identical rails ready
to use are provided in one single cutting operation. Fastening apertures 11,22,
respectively will then be provided in a conventional manner in the vertical side
walls in the vicinity of the provided reinforcing rib 3.
Fig. 1b shows an alternative cross-sectional configuration of the
intermediate extruded shape comprising two co-extruded rails 1,2 where the reinforcing
rib 3 protrudes laterally from both sides of the vertical rail wall 4.
Another variant of the intermediate extruded shape illustrated in
Fig. 1c exhibits no reinforcing rib between the co-extruded rails 1,2.
This particular embodiment will, after applying the above cutting
pattern described in connection with Fig. 2, also result in two identical rails
exhibiting different heights along their longitudinal extension and where the "elevated"
part of the rails represent a local reinforcement of the rail in the area of fastening
apertures (not shown in the Figure).
There is also a possibility to conduct "an asymmetric" longitudinal
cut so that two rails having different longitudinal extension of the elevated part
can be provided in one operation without spill of the material.
Still another configuration of the extruded intermediate shape is
shown in Fig. 1d. Two rails of non-identical cross-sectional configuration 1,2
are co-extruded comprising in common a reinforcing rib 3 laterally protruding from
the vertical rail wall 4.
An apparent advantage of this alternative configuration is the possibility
to provide two different rails in a simple step cutting operation by the alternating
movement of the cutting tool along the upper and the bottom side of the reinforcing
Fig. 3 illustrates in a perspective view the special design of the
resulting rail applied as a top rail 1 comprising a higher part provided with the
laterally extending top rib 3 representing the reinforced part of the rail exhibiting
fastening apertures 11 for safety belts.
A perpendicularly movable locking means 5 ensures in a conventional
manner attachment of the top rail 1 to the bottom rail 7.
The new method of manufacturing seat rails as illustrated above by
way of examples of cutting different embodiments of the intermediate extruded shapes
according to the present inventive principle results in a reduced number of processing/manufacturing
steps, less use of material and consequently in substantial costs savings.