Cast molded seat unit for motor vehicles

Details Cast molded seat unit for motor vehicles Cast molded seat unit for motor vehicles

1998-03-03

2001-07-10

Pape, Joseph D. (Department: 3612)

Land vehicles: bodies and tops

Bodies

Seats with body modifications

C296S065140, C296S065150, C248S429000, C297S473000

Reexamination Certificate

active

06257642

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a seat unit for motor vehicles.
BACKGROUND OF THE INVENTION
The term “seat unit” is defined as any part of a vehicle seat which has at least two seat elements. Seat elements means all elements which belong to the structural and/or functional design of a vehicle seat including fixing and adjusting mechanisms. In particular, two rail devices for longitudinally adjusting the seat are seat elements.
From DE 37 03 515 A1 a seat unit is known where a bearing on the floor side has upper and lower rails whereby the seat can be moved forwards and backwards. The seat frame supporting a seat cushion is connected to the separated upper rails of the bearing by guide rods which are provided in the front and rear areas of the seat. Apart from longitudinally adjusting the seat, smooth-changing gears allow the height of the seat, as well as the incline of the seat, to be adjusted. These gears are fitted on the seat frame. The disadvantage with this construction is the number of individual structural elements which have to be fixed on the upper rail. This leads to relatively high production costs.
In DE 44 19 139 a device is disclosed in which the number of structural parts on the upper rail is limited. To this end, a frame construction is provided for the seat of a vehicle with a seat surface part, a backrest part and support parts for supporting the seat surface part on a rail structure mounted on the vehicle floor in the longitudinal direction of the vehicle. The support parts are formed in one piece as aluminum extruded pressed profiled parts with structural elements running in the longitudinal direction of the vehicle. Bulges are formed crosswise to the profiled plane to reinforce the profiled part against bending around an axis parallel to the longitudinal direction of the profile.
With this proposal the number of structural elements required for fixing the seat on the rail structure is reduced, however, all the additional elements (e.g., guides and gears for a longitudinal and height adjustment of the seat) must also be additionally fixed on the frame structure. Indeed, the fixing means for the individual structural parts (e.g., bores or milled areas) must generally be made by a second work step which takes place after the extrusion pressing.
From DE 94 12 155.9 U1 a rail guide is known which has two relatively displaceable rails in which one rail supports plastics-coated teeth extending along the displacement path into which a drive worm connected to the other rail engages through further gearing elements. The outer contour of the plastics-coated teeth, which consists of toothed elements or a toothed rod, corresponds to the contour of the engagement area of the drive worm teeth which are formed as inclined teething. The plastics-coating straight teeth, made by punching, can be converted into inclined teeth to produce a permanent surface contact with the worm.
A disadvantage with this solution is the expensive manufacture and number of work steps required to produce the inclined teeth.
From DE 196 17 877 A1 a rail guide is known which comprises two rails which can be displaced relative to each other in the longitudinal direction, and a gear housing connected to one of the rails by fixing means. In detail, a gear housing, connected to the first rail, is displaceable across the longitudinal direction of the rails for the purpose of adjusting play in the seat and can be locked in a position where the teeth of one displacement worm mounted in the gear housing engages with the teeth of the second rail. With this solution the two separate elements (gear housing and rail) have to be connected together by a separate fixing means which is a disadvantage.
SUMMARY OF THE INVENTION
The object of an embodiment of the present invention is to provide a seat unit where the configuration of the individual parts of the seat unit can be optimized to the anticipated load conditions, and where the number of parts of the seat unit is reduced.
According to a preferred embodiment of the present invention, at least two of the seat elements of one seat unit (e.g. elements of a seat length adjustment, seat side parts and seat shell) are formed in a one-piece cast part. Cast part preferably means any part which is made by casting using a casting mold. In addition to the standard casting process, injection or pressure casting is also a satisfactory approach. The manufacture of at least two of the seat elements as a cast part can be carried out in a simple way by means of suitable casting molds.
The manufacture of seat elements as cast parts, and more particularly a rail unit for motor vehicle seats, goes against popular opinion in the technical world that economic production would not be possible owing to the very expensive casting molds which would be required. And even if the cast parts could be manufactured economically then, in the opinion of the technical world, they would have to be made with increased wall thicknesses owing to their brittle nature and this would lead to increased weight. Moreover, they could not withstand greater stresses, for example, in the case of a crash. For this reason rail devices for motor vehicle seats have been made up until now by extrusion pressing or the like.
A preferred embodiment of the invention is based on the premise that by using a suitable casting mold a number of seat elements can be molded in a simple way on a seat element which is formed as a cast part, and more particularly on a rail device. The number of seat elements of a vehicle seat, and thus also the number of connecting means, can thereby be reduced. Furthermore tolerances are avoided which normally occur at the connecting points. The individual molded seat elements can have walls of different thickness and recesses so that the stability is guaranteed at all critical points of the seat unit and the weight can be minimized at the same time. Being formed as a cast part, the individual parts of the seat unit can be designed to optimize anticipated load conditions.
In a preferred embodiment of the invention the seat unit has a guiding rail unit fixed on the vehicle and a movable rail unit displaceably guided along the guiding rail unit. At least one of these rail units is formed as a cast part wherein additional seat elements are connected in one piece by casting to its respective rail unit formed as a cast part.
In a further embodiment of the invention, the additional seat elements molded in one piece on the rail unit comprise component parts of a seat adjustment device. By way of example, a gear housing, which is provided to hold an adjustment gear for a seat length adjustment, is molded in one piece on the rail unit formed as a cast part. The advantage of such a design is the reduction in the number of structural elements which can be manufactured in one piece in one easily implemented casting process with a suitable casting mold. This procedure avoids any type of fixing means which would have to be used to connect individual structural parts together. This leads to an efficient manufacturing process and to a simple assembly of the seat unit.
In order to improve the sliding properties of an adjusting gear located in a housing for the seat length adjustment according to a preferred embodiment and the present invention, teeth are provided preferably running on the first rail unit in the longitudinal direction of the rail while the housing for the adjusting gear is preferably molded on the second rail unit (e.g., the upper rail). The teeth of the first rail unit are preferably formed as inclined teeth so that they are adapted to the contour of the teeth of the adjustment worm of the adjusting gear. More particularly, the inclined teeth can be made directly during casting which cannot be achieved with the conventional extrusion pressing process.
In a further embodiment of the present invention the rail unit formed with teeth has a first web with inclined teeth and a second web with straight teeth. The adjustment worm only meshes with the inclined teet

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