Thin, double-wall molded seat frame system
A seat frame for a vehicle or other seating comprises a seat back and a seat pan formed of molded double wall members having thin, substantially closed exterior walls and a substantially open interior. The exterior walls include front and back sections having a cavity therebetween, secured together to form a hollow, box beam type of structure. Integrally formed, spaced cup-shaped standoffs extend between the front and back sections between side walls thereof and provide internal reinforcement of the seat member between the side walls. The seat back includes a cavity for a seat back reinforcement member for either a restraint or non-restraint seat.
This application is based on and claims the benefit of the filing date of co-pending U.S. Provisional Patent Application Ser. No. 61/237,926, entitled Thin, Double-Wall Molded Seat Frame System and filed on Oct. 4, 2000, by Patrick M. Glance and Bradley M. Glance, the disclosure of which is incorporated here by reference.BACKGROUND OF THE INVENTION
The invention relates to vehicular seating generally and more particularly to a new vehicular seat frame.
Today automotive seat frames, for example, are constructed from a number of materials and manufacturing technologies. Most seat frames and seat backs are fabricated from steel tubing. Front bucket seat pans (a lower seat frame utilized to mount a seat lower cushion) are commonly stamped steel with a steel seat spring suspension, although a technology limitation of steel seating frames is their large mass. Some seat frames utilize aluminum or magnesium, which has lighter mass, but is more expensive. Some seat pans are molded, glass-filled polypropylene or other molded resin systems.
Many automotive rear folding seats are blow molded, high-density polyethylene, or other resin. Some rear folding seat backs that double as a load floor in a down position, are compression molded, glass filled polypropylene, blow molded high density polyethylene, blow molded ABS/polycarbonate, or other resin system. Some front seat back frame/trim covers are also molded glass filled polypropylene, polycarbonate, or other resin.
A technology limitation of molded seat frames is their relatively large molding thickness, typically about 3 mm with ranges from about 6 to about 2 mm. The large molding thickness results in a slow molding cycle time, and greater material usage, which directly results in a higher seat frame cost. A low resin tensile strength also contributes to larger molding thickness that is required to meet structural seat back load requirements. This is a technology limitation and natural consequence of plastic seat frames.
These technology limitations have resulted in steel seat back frames weighing 6 to 8 pounds and costing $8 to $12, while steel bucket seat frame assemblies weigh between 4 to 6 pounds, and cost between $4 to $6. Aluminum fabrications are usually half the mass, but double the cost of steel. Magnesium frames usually cost more than aluminum.
Molded seat frames are typically expensive compared to steel frames, but are utilized for specialty, niche applications where the molded surface doubles as a styling show surface, a load floor, or is utilized to reduce mass in conjunction with metal reinforcement. Molded seat frames often have a lower mass than their steel counterparts, at a higher cost. Lower mass is useful in improving vehicle fuel economy and may be a factor in the safety consideration.
Of course, the above comments assume that all the seat frame alternatives are designed to the same or similar structural requirements. Regardless, a need for an alternative construction that reduces mass at no cost penalty is clearly desired.BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, a molded seat frame that lowers mass compared to conventional metal, but is cost competitive, comprises a thin, double-wall injection molded seat frame system. Theoretical studies indicate that a double wall injection molded, talc-filled high density polypropylene seat back, molded in a 1 mm wall thickness, will result in a 60% mass reduction, and a 25% cost reduction versus current technology steel frame systems. The key to this savings is the use of the design principle of a closed box section with a thin wall structure that has continuous design stand-offs between the double walls to resist “thin wall buckling.”
The large area enclosed in a continuous jointed container is an extremely strong and efficient structure, especially during torsional loading. The characteristic analogy in nature is an eggshell, but with added integral, inter-connecting “stand-offs” to reinforce the thin outer shell, and improve structural strength.
A basic principle of this invention is the use of a thin wall enclosed structure that is molded from two halves and jointed to create a structure with internal reinforcements either molded-in or “placed” in the structure. This approach has advantages for improved product simplification, reduced mass, improved structure, and incorporation of dissimilar materials and reinforcement within the assembly.
For example, one design scenario is the use of an injection molding 1 mm thick, filled plastic in a half cavity shape. At the same time, a corresponding 1 mm half cavity shape may be molded and then the two joined by hot plate welding, sonic welding, bonding, or other joining technology. The injection molded two half design approach produces a product that is similar to a blow molded seat frame construction, but the injection molding has further advantages of better component thickness control, thinner wall, faster cycle time, and use of larger varieties of resins. It is possible to mold resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), thermosets, and glass-filled nylon, for example, which cannot be blow molded. The basic design concept also has application for metal die casting, such as zinc and magnesium and vacuum injection molding.
Although the invention is described for automotive or over land vehicular seating, the basic invention has application for all vehicular seating applications including without limitation air, marine, bus, and rail. The invention may also be applied to office, home, and theatre seating, for example. The specific design sketches are for bucket seating, but the same principle applies for bench seating and couches.
These and other features, objects, and benefits of the invention will be recognized by one having ordinary skill in the art and by those who practice the invention, from the specification, the claims, and the drawing figures.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
A preferred embodiment of a thin, double wall molded seat frame system according to the invention is generally shown in the drawing figures and discussed below.
Referring to the drawings,
A reinforcement tower 18 extends through an internal cavity 20 on one side of the seat back. In
Seat pan 14 comprises a generally rectangular frame having a front frame member 26, a rear frame member 28, and side frame members 30, defining an open interior portion 32. A conventional resilient insert 34 can be inserted in opening 32. The insert may be formed of conventional insert material, the insert being conventional.
Side frame member 30 and rear frame member 28 include reinforcement ribs 36 in an upper surface thereof. The seat pan has recessed fastener attachment areas 38 in the corners thereof for attaching the seat pan to a seat support structure in a vehicle. Front frame member 26 has an elevated contoured portion 40 that provides a desirable contour for leg support at the front edge of the seat pan.
The construction of the seat pan 14 is shown in more detail in
Upper section 42 has an upper surface 46, outer sidewall 48, and inner sidewall 50, with the rear side of the upper section being open. Lower section 44 covers the open rear side of the upper section and has flanges 45 and 47 at inner and outer peripheral edges that engage and are secured to the sidewalls of the upper section to form a closed box beam.
Independently spaced, conical, cup-shaped projections 52, preferably with a circular cross section, extend downwardly from the upper surface of upper section 42 in the interior of the front and rear members 26 and 28. These form standoffs that reinforce the interior portions of the seat pan. The standoffs in the upper section of the seat pan desirably are opposed by corresponding standoffs 54 that extend upwardly from at least the front portion of lower frame section 44. Lower standoffs 54 can also be upwardly extending cup-shaped conical projections. The lower projections are shorter than the upper projections in the illustrated embodiment. The ends of the conical projections can abut each other, as shown in
Desirably, the seat pan is formed by injection molding, although other molding techniques will work. A satisfactory resin for the present invention is a talc-filled high density polyethylene (HDPE), but other materials are satisfactory.
The construction of seat back 12 is shown in
Cup-shaped standoffs 90 are formed between the sidewalls at various locations in order to provide internal reinforcement for the seat back at positions between the sidewalls. In the illustrated embodiment, the standoffs are generally rectangularly shaped, with opposing standoffs being formed on the inner sides of the back and front sections. The standoffs may abut each other and be fastened together when the opposed sections of the seat back are fastened together. It is contemplated that the standoffs could be in one section or the other but not both sections in appropriate cases.
The seat back of the present invention is formed in the shape of a rectangular frame having side members 92, bottom member 94, and a top member 96. Desirably, an integral head rest 98 is mounted on the top of top member 96. The integral head rest includes side members 100 and a top member 102 extending between the tops of the side members. An opening 104 is formed in the interior of the head rest. Similarly, an opening 106 is formed in the interior of the seat back 14. An insert 108 formed of a plastic rattan material or other flexible material can cover the opening 106. An attachment flange 110 can surround the interior edge of opening 106 for attaching the rattan insert or the like. The attachment flange can be formed of an elastic material such as a Flex-o-lator brand product.
One of the side members 92 of the seat back can have a hollow tower insert cavity 20 therein for insertion of either a restraint tower 18 or a non-restraint tower 24. The restraint towers desirably are formed of aluminum tube. A restraint tower is somewhat thicker than a non-restraint lower, with the restraint tower desirably being 2.2 mm thick and the aluminum material in the non-restraint tower being about 1 mm thick.
With the seat back and seat pan formed in the foregoing manner, the seat has a desirable outer configuration and an inner configuration that facilitates mounting in the vehicle, and yet the structure is lightweight, strong, and relatively inexpensive.
A particular bucket seat assembly is shown in the present invention. It should be understood that various other types of seat configurations could be employed without departing from the spirit and scope of the present invention.
Among the advantages of the present invention, the seat is a hollow, internally reinforced, integrated structure created from two molded cavities which are joined together to form a closed section container shape. This provides desirable strength, weight, and expense characteristics.
Another advantage of the present invention is that the seat frame pan and seat back are formed in two cavity halves, which are molded together to form a closed box section. It is desired that the walls of the two cavities, in each case, are relatively thin (typically about 1 mm) and hence flexible, with internal, molded standoffs reinforcing the outer walls when the two cavities are joined together. Notwithstanding the extremely thin walls, the seat frame pan and seat back provide good structural performance.
The seat frame pan and seat back can be formed from a number of different manufacturing processes, such as injection molding, twin sheet vacuum forming, vacuum die casting, casting, or compression molding. The seat frame pan may be formed of a number of different materials, such as high density polyethylene, polypropylene, acrylonitrile butadiene styrene, polycarbonate, sheet molding compound, PBT, PET, or metal such as magnesium, zinc alloy, or aluminum. Talc filled HDPE is typical. The seat back can be made of comparable materials.
As shown in
It will be understood by one having ordinary skill in the art and by those who practice the invention, that various modifications and improvements may be made without departing from the spirit of the disclosed concept. Various relational terms, including left, right, front, back, top, and bottom, for example, are used in the detailed description of the invention and in the claims only to convey relative positioning of various elements of the claimed invention. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.
1. In a seat frame comprising a seat back and a seat pan, the improvement wherein at least one seat member of the group consisting of the seat pan and seat back comprises a molded double wall member having a substantially closed exterior wall and a substantially open interior, with the exterior wall comprising opposed front and back sections having a cavity therebetween, the front and back sections fitting together and being secured together to form a hollow, box beam type of structure.
2. A seat frame according to claim 1 wherein at least one of the front and back sections includes integrally formed, spaced cup-shaped standoffs extending between the front and back sections at positions between the side walls thereof, such that the standoffs provide internal reinforcement of the seat member between the side walls.
3. A seat frame according to claim 2 wherein the standoffs include individually formed, conical, cup-shaped energy absorbing cells.
4. A seat frame according to claim 3 wherein aligned standoffs are formed in the back and front sections, such that inner ends of aligned standoffs are adjacent each other when the front and back sections are interconnected.
5. A seat frame according to claim 1 wherein the at least one seat member comprises the seat pan, the seat pan being formed in a generally rectangular shape and having a hollow peripheral frame comprising a front member back member and side members, the frame having an open interior, the front, back, and side members being box beam members formed of the front and back sections, the front section being an upper section and the back section being a lower section, the frame including interior standoffs extending vertically between the upper and lower sections.
6. A seat frame according to claim 1 wherein the at least one seat member includes the seat back.
7. A seat frame according to claim 6 wherein the seat back includes a hollow cavity for a seat back reinforcement member.
8. A seat frame according to claim 7 wherein the cavity is formed along a vertical side of the seat back and is shaped to receive a seat back reinforcement tower formed of a material dissimilar from the seat back.
9. A seat frame according to claim 6 wherein the seat back comprises a generally rectangular frame having upper and lower frame members and side frame members, with each frame member having a box beam configuration with a substantially hollow interior, the frame having interior standoffs reinforcing front and back surfaces of the frame between frame side walls.
10. A seat frame according to claim 9 wherein the standoffs include spaced, cup-shaped energy absorbers mounted in at least one of the front and back members and extending in a direction between the members.
11. A seat frame according to claim 1 wherein a plurality of standoffs are formed on the interior of one of the front and back sections of the seat back, the other of the front and back sections of the seat back including standoffs that are aligned with the standoffs in the one section, outer ends of the aligned standoffs being substantially abutting each other, the standoffs comprising elongated, hollow projections.
12. A seat frame according to claim 9 wherein the frame has at least a partially open portion interior of the frame members, the frame members surrounding the open interior.
13. A seat frame according to claim 1 wherein the front section is contoured for serving as a support for the body of a person seated in the seat, while the back section is provided with a different surface contour that is designed to provide an acceptable configuration for attachment in a vehicle, the different surface contours not requiring substantial additional material in the seat member because of the hollow seat member construction.