Seat and method of manufacture

Abstract

The seat comprises a cushioning unit having a shaped profile member 150 and a pocketed spring unit 140 arranged to at least partly adopt the shape of the profile member. A spring of the pocketed sprin

Description

The present invention relates to a seat, and to a method of manufacturing a seat, and is concerned particularly, though not exclusively, with a vehicle seat and a method of manufacturing a vehicle seat. Most seats, such as those used in passenger vehicles, are shaped in some way for the comfort of the user. For example, the seat base may have a cushioned unit in its centre and raised edges or sides for additional support. A seat back may be shaped for the same reason. The sides are also preferably cushioned. To achieve the desired shapes, the manufacturers of many existing vehicle seats utilise a high density open-cell foam, such as polyurethane foam. Whilst the foam components possess the desirable qualities of resilience and low weight, they are difficult to recycle and often go to land fill, which is wasteful and environmentally unsound. There has recently been a return to using springs, such as metal coil springs, in the manufacture of vehicle seats. However, positioning and containing individual springs in a seat is difficult and time consuming, whilst previously considered pocketed spring units, such as are described in our European Patent Number EP1993947 (Bl) are flat and cannot be shaped to provide the desired seat profile. Embodiments of the present invention aim to provide a seat and a method of making a seat, particularly suited to passenger vehicles, in which the aforementioned problems are at least partly addressed. The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto . According to one aspect of the present invention, there is provided a seat comprising a cushioning unit having a shaped profile member and a pocketed spring unit arranged to at least partly adopt the shape of the profile member. Preferably, the pocketed spring unit comprises an array of springs located in pockets formed by common superposed plies of pocketing material joined together at locations between the springs . Alternatively, or in addition, the pocketed spring unit may comprise a resilient unit comprising a body and a number of resilient elements, such as springs, wherein the body comprises a block of resilient material and wherein the or each resilient element is located within the block. In a preferred arrangement, the seat comprises one or more cushioning pads or panels positioned over the pocketed spring unit. The seat may comprise a support base for supporting the profile member. Preferably a cover is arranged over one, more than one or all of the pad(s), the pocketed spring unit, the profile member and the base. The cushioning unit may comprise a seat base. Alternatively or in addition, the cushioning unit may comprise a seat back. The seat may have a first cushioning unit as a seat base and / or may have a second cushioning unit as a seat back. The profile member may comprise a moulding and may be of plastics. More preferably the profile member comprises expanded polypropylene (EPP). The or each cushioning pad / panel may comprise one or more of (but is not limited to): spun-bonded polyester, a non-woven, wool, hemp, flax or spacer fabric. The support base may comprise metal or plastics. The support base may be integral with the profile member. The or each spring preferably comprises a compression coil spring, more preferably of metal wire. In a preferred arrangement, one or more of the springs has at least a dual rate of compression. Preferably, one or more of the springs has a soft start characteristic, such that a lower force is required to effect an initial phase of compression whereas a greater force is required to effect a later phase of compression. The or each spring may comprise spring portions, preferably integral spring portions, having coils of different pitch or spacing. In a particularly preferred arrangement, one or more springs has an upper region in which the coils are of closer or lesser pitch and a lower region in which the coils are more spaced or of greater pitch. One or more of the components may be fixed, bonded or adhered together . The seat preferably comprises a vehicle seat. According to another aspect of the present invention, there is provided a method of making a seat, comprising a cushioning unit, the method comprising supporting a pocketed spring unit against a shaped profile member, causing the pocketed spring unit to at least partly adopt the shape of the profile member. Preferably, the pocketed spring unit comprises an array of springs located in pockets formed by common superposed plies of pocketing material joined together at locations between the springs . The method may include placing one or more cushioning pads or panels over the pocketed spring unit. In a preferred arrangement, the method comprises supporting the profile member on a base, which base may be substantially rigid or semi-rigid. The method may include substantially encasing one, more than one or all of the pad(s), the pocketed spring unit, the profile member and the base in a cover. The method may include making a seat using the cushioning unit as a seat base. Alternatively, the method may comprise making a seat using the cushioning unit as a seat back. In a preferred arrangement, the method comprises making a vehicle seat. The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows, in a schematically exploded view, a part of a seat according to an embodiment of the present invention; Figure 2 is a schematic cross-section of a part of a pocketed spring unit as used in the seat of Figure 1; Figure 3 shows schematically a cross section of an alternative pocketed spring unit; 5 Figure 4 shows schematically an exploded view of an alternative embodiment of seat, according to the present invention; Figure 5 shows schematically a part of another alternative 10 spring unit; and Figure 6 represents graphically the force versus the deflection (compression) of a spring of the unit of Figure 5. 15 Turning to Figure 1, this shows generally at 100 a seat base in schematic exploded view. The seat base is suitable for a seat used in a passenger vehicle, such as a vehicle seat. 20 The seat base 100 comprises a cover 110, a first overlying pad 120. Side pads 130a, a front pad 130b, a pocketed spring unit 140, a shaped profile member 150 and a support base 160 . 25 Figure 2 shows schematically a cross-section of a part of the pocketed spring unit 140. The pocketed spring unit is resiliently compressible and comprises an array of metal coil springs S, in individual pockets formed by axially superposed plies, or sheets, 142 of non-woven, spun-bonded 30 polyester that are joined by ultrasonic welds at positions 144 between the springs and along the edges of the unit. Other spring units may be used, instead or in addition. For example, a resilient unit comprising a body and a number of 35 resilient elements, such as springs, wherein the body comprises a block of resilient material and wherein the or each resilient element is located within the block may be used. The first and second pads / panels are preferably any one or more of (but not limited to) spun-bonded polyester, nonwoven, wool, hemp, flax or spacer fabric and are resiliently deformable . The profile member gives the seat base its shape and has a substantially flat central portion 150a flanked by raised side portions 150b. The profile member can advantageously be of EPP and may comprise a moulding. A rigid, or semi-rigid, base supports the entire structure and comprises a sheet of plastics, metal, such as aluminium or an alloy, or else of wood. The cover is of a wool-based, stretchy material such as Moquette and encloses all the other components when assembled, keeping them in alignment. The overall shape of the seat base is determined by the profile member 150 and the pocketed spring unit, being flexible out-of-plane, adopts this shape, so that the benefit of the resilience of the pocketed springs may be felt by someone sitting on the seat both in the central part and also in the side portions. The pads 120 and 130 also adopt the shape of the profile member 150. Figure 3 shows an alternative pocketed spring arrangement. In this example, the springs S' are designed to have at least a dual rate of compression, i.e., the compression characteristic of the spring overall has at least two compression phases, wherein the spring compresses at a first rate in a first phase and compresses at a second rate in a second phase, for the comfort of the user. In the example shown, this is achieved by varying the pitch of the coils of the springs. However, a similar effect can be achieved for example by selecting / varying one or more of the shape of the spring, the length of the spring, its diameter, the thickness of the wire and / or the rate at which air is displaced from the pocket. Alternatively, or in addition, springs may be combined with other springs, such as by superimposition or nesting the springs, to provide the required compression characteristic . Zoning of the springs within the pocketed spring unit, for example by arranging springs with different characteristics in different parts of the spring unit, may also be utilised. Figure 4 is an end view of part of the seat showing the pocketed spring unit 140 extending not only over the base 150a of the shaped profile member 150, but also partly over the raised flanks 150b. The pocketed spring unit 140 adopts the shape of the profile member 150, in this case giving a "dished" shape to the pocketed spring unit 140. The spring unit 140 stops short of the edge of the profile member 150 so that the pads 130(a) can form a border. The cover is omitted from this drawing for clarity. Figure 5 shows schematically part of another alternative spring unit 240. Similar to the springs S' of the arrangement 140 of Figure 3, the springs S' ' of Figure 5 have a dual rate of compression. In this case the dual characteristic is known as a "soft-start". An upper part A of the spring comprises coils that are of closer, or lesser pitch, whereas a lower part B of the spring comprises coils that are spaced further, or are of a greater pitch. The effect of this is two-fold. In an early part of the compression of the springs S'' the force required to compress them is less, whereas in a later part of the compression, a greater force is required. A user experiences an initial yielding of the seat, followed by a supportive firmness. Another benefit of the softer characteristic of the upper part A is that the seat cover remains in mild tension, as it is pressed mildly by the upper coils, and thus maintaining a pleasing appearance, without placing the cover under excessive pressure, which could cause it to sag over time. Figure 6 is a schematic graph of the force (Y-axis) needed to compress the springs of Figure 5, versus the extent of deflection / compression (X-axis). It can be seen that in the early stage of compression only a slight increase in applied force is needed, as the upper coils compress. In a later stage of compression, the force required to compress the lower coils is greater. Of course, different spring characteristics could be used to achieve a different effect, including ones with multiple phases of compression or a progressively changing stiffness. The example shown is of a seat base, but a seat back could be formed in a similar way. Seats according to the present invention may find use in a range of situations. Whilst the primary use is intended to be in vehicles, such as automotive, rail, aeroplanes and ships, the seats could also be used as furniture in a variety of settings. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and / or shown in the drawings, whether or not particular emphasis has been placed thereon.

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