US 3175863 A
Description (OCR text may contain errors)
March 1965 B. G. HOOD 3,175,863
UPHOLSTERED CHAIR OF MOLDED URETHANE FOAM Filed June 24, 1963 INVENTOR.
United States Patent 3,175,863 UPHOLSTERED CHAIR OF MOLDED URETHANE FOAM Bruce G. Hood, Marblehead, Mass, assignor, by mesne assignments, to Davidson Rubber Company, Incorporated, a corporation of Delaware Filed June 24, 1963, Ser. No. 289,809 3 Claims. (Cl. 297-455) This invention is an upholstered set member molded from low density urethane foam, such as a chair or sofa.
The upholstered seat member consists of. an integral or monolithic core of rigid urethane foam defining the base, the back rest and at least one arm member. The body contacting surfaces of this core are covered with a well-bonded layer of soft, flexible and resilient urethane foam. The visible outer surfaces of the seat member are covered with a suitable tough covering not only for the purposes of appearance but also because the covering prevents local damage to and tearing of the urethane foam.
Besides its aesthetic appearance and comfortable upholstered nature, the seat member of this invention is characterized by the simplicity of its elements which greatly simplifies the manufacturing procedure and permits mass production. It is also characterized by its light weight while still having good abuse resistance and strength.
In a preferred design of this invention, the back rest and arm rest flow smoothly together to form a generally cup-shaped side and back supporting wall. This design is such that maximum advantage is taken of the structural strength of the urethane foams.
The nature and advantages of the seat member of this invention will become clear from the following description and examples made with reference to the drawings attached to and forming a part of this specification.
In the drawings:
FIG. 1 is a perspective view of a completed chair;
FIG. 2 is a front elevational cross-section view taken along line 2--2 of FIG. 1;.
FIG. 3 is an enlarged view of a corner section of the supporting core of the seat member showing a densified outer skin;
FIG. 4 is an enlarged crosssectional view of the lower edge of the core showing inclusion in the core of a tacking strip for purposes of anchoring the upholstery covering; and
FIG. 5 is an enlarged cross-sectional view of the bottom edge of the core showing inclusion in the core of strengthening and fastening means for permitting attachment of the supporting legs to the chair.
Rigid urethane foams have, generally speaking, been regarded as being essentially weak, friable materials useful mainly for filling voids or where lightness and insulation values are important, but not strength. In the seating member of the present invention maximum adva11- tage is taken of the strength of a rigid urethane foam core in cooperation with a surface covering of a soft flexible urethane foam. In bulk, rigid urethane foams can be quite strong but if a high local pressure is applied to the surface of a rigid urethane foam it tends to collapse and leave an indentation. receiving or body supporting surfaces of the urethane core member are protected by being covered with a resilient but fairly strong layer of flexible urethane foam. This In the present invention the wear structure.
flexible urethane foam covering is tougher than the rigid urethane foam core and serves to distribute any pressure applied to it over a wider area of the rigid urethane core. The flexible covering has, of course, more impact resistance than the urethane core and serves to prevent damage to the core member when it is forcibly struck. The flexible urethane covering is well bonded to the wear receiving surfaces of the urethane core to prevent slippage and looseness and to have the urethane core in turn impart strength to the flexible urethane covering.
In addition to the cooperative relationship between the flexible covering and the rigid core, the wear receiving surfaces of the upholstered unit are additionally covered with a strong decorative outer covering such as a vinyl covering or one made from fabric. Flexible urethane foams have a relatively low tear resistance or Table I presented hereinafter summarizes the pre ferred properties of the urethane foams used in the practice of this invention, and gives examples thereof.
Specific formulations are presented in Table II.
Referring to the drawings, the seat member of this .invention consists of a molded core 10 of rigid polyurethane foam. This core defines the base 10a of the seat member, the arm rest 1% and the back rest. The hole of the core is integral or monolithic. Since the rigid urethane foam is incapable of resisting a high localized pressure, a reinforcing member 11 which extends over a considerable portion of the underside of the base is integrally molded into the core structure and is adapted to receive the supporting legs 12 for the chair. Reinforcing element 11 may be a solid wood piece as shown in FIG. 2, or as shown in FIG. 5 can be a relatively heavy screen 11a which also can be used to receive screws 13 by which legs 12 are attached.
The molding of the core is quite straight forward. The formulation given in Table II is a room temperature curing formulation. An enclosed mold of suitable design is fabricated and the urethane ingredients are mixed and promptly injected into this mold and the mold is closed. Foaming occurs immediately with some exotherrn. With the formulation of Table I the reaction will be complete in about twenty minutes for this size One feature of this invention is the provision for a tough skin on the outer surfaces of the core having a higher density than the foam in the interior of the core. This is shown in FIG. 3. The denser skin is shown at x and the lighter interior core at y. Skin 2: has a thickness of about 0.06 inch and is at least two times the density of the core y. This is achieved by chilling the outer surfaces of the mold so that the expanding foam when its contacts the interior walls of the mold is chilled causing the blowing agent either to remain liauid or to exert a lesser expansive force.
As indicated previously, the core in itself will not take too much abuse on its wear receiving surfaces. For this reason and for the purpose of providing an upholstered feeling, the wear receiving or body supporting surfaces of core 10 are covered with a resilient flexible urethane foam 15, the formulation of which is given in Table II. This layer 15 can be derived from slab stock if the surface of the core 10 is amenable to being covered in this manner. A good adhesive such as Empire Adhesives R-l04l-2 should be used to secure tight bonding of the be less than 2.50 inches in order to have adequate strength.
The minimum thickness of the flexible padding in any cross-section should be 0.75 inch. This is not only from the standpoint of resiliency and comfortable feeling but also to provide suflicient depth to permit the flexible foam layer 15 to distribute local pressure more uniformly on the core.
The completed unit is covered on all its visible surfaces, i.e., except on the underside, with a fabric of synthetic fabric covering 16. The fabric is mounted by stretching it over the chair surfaces and attaching it to the underside of the base. In the preferred embodiment of this i invention the underside of the base has tacking strips 17 extend across the upper surface 21 of core to provide a sitting pad.
In the design shown, however, a separate cushioning element 23, also molded of flexible urethane foam and coveredwith fabric 16, is used for this purpose.
It matches the contour of the basic chair unit. In this arrangement, fabric 16 need not extend over all of surface 21, although this is preferred.
The particular design of chair shown in the drawings is preferred because it takes maximum advantage .of the strength olfer'ed by the'urethane foams. It will be noted that when viewed from the top it is of generally semicircular configuration with the back rest coming up to about themid-point of the person sitting in the chair. The backrest and arm members smoothly flow together to forin one continuous integral unit. The top surfaces of the arms are downwardly inclined towards the front of the chair. The supporting core member when viewed in cross-section from the front has the appearance of an upwardly opening thick-walled channel with the walls being outwardly inclined. The inner side walls of the arm rest and back rest have a funnel shape.
It can be appreciated that this semi-circular configuration permits the stresses on the chair occasioned by a person sitting in it and leaning back to be relatively uniformly distributed over the foam structure. The upper horizontal surface of the back rest-arm rest configuration provides adequate comfortable support for the arms of a person sitting in the. chair. This clean, modernistic free flowing design is considered to be a distinguishing feature of this invention and represents a preferred em- 'bodiment thereof.
TABLE I Properties of foamed urethanes Range Example Rigid Core (AS'IM Test):
Density, lbs/ft. 4 to 20 5 to 6 Tensile strength, p.s.i. (D638) 20 to 40.-.. 30 to 40 Compression strength, p.s.l. (yield point) to 30. to Flexural strength, p.s.l. (ASTMD790) 20 to 60"-. to Minimum section thickness, inches 2.5 to 7 3 to 7 Cushioning Layer:
Density, lbs/It. 0.9 to 6 1.5 to 4 Elongation, percent (D638). 100 to 350 150 to 250 Tensile strength, psi. (D63 5 to 4') 10 to 80 RMA firmness, 25% deflection 15 to 25 Resilienrtzy (Nopco tester ball rebound), 40 to 60 to percen 4 TABLE 11 Urethane formulations Core formulation (parts by weight):
Polyglycol-A 1 95.0 Toluene diisocyanate 2 72.5 Blowing agent 25.0 Lubricant 4 2.0 Curing agent 0.5
Cushioning layer formulation (parts by weight):
Polyglycol-B 1 100.0
Toluene diisocyanate 2 46.3 Blowing agent 3 3.0 Lubricant Curing agent 5 0.24 Tin catalyst 0.24 Water 3.4
Polyglycol-A (Atlas Powder G-2410) is a sorbitol based hexanol having a hydroxl number of approximately 490.
Polyglycol-B (Wyandotte Chemical Plurecal TP2540) is a polyoxypropylene triol derivative of trimethylolpropane having a molecular weight of 2670 and a viscosity of 440 cps. int 25 degrees C.
2 A commercial mixture of of the 2,4 isomer and 20% of the 2,6 isomer.
3 Difluoro-dichloro methane (Freon-11).
4 Silicone (Union Carbide Corp. Silicones Ir-520).
5 Triethylenediamine (I-Ioudry Process 00.).
G T-S) (Metal 8: Thernrit Corp).
Other rigid and flexible urethane formulations can, of course, be used so long as they meet the given in Table I.
Having described this invention what is sought to be protected by Letters Patent is succinctly set forth the following claims.
1. An integral upholstered seat member comprising a supporting monolithic core of rigid urethane foam free soft flexible layer of urethane foam bonded to the body contacting surfaces of said back rest and said arm rest and a decorative flexible and protective covering over the visible'surfaces thereof other than the underside of said base, said rigid urethane foam having a density in the range of 2.5 to 5 lbs. per cubic feet, a flexural strength in the range of 20 to 60 p.s.i., and a minimum thickness in cross-section at any point of 2.5 inches, and said soft flexible layer having a density in the range of 1.5 to 6 lbs. per cubic foot, an elongation in the range of to 350 percent, a tensile strength in the range of 5 to 40 psi. and a RMA firmness at 25% deflection in the range of 5 to 35.
2. The seat member of claim 1 having two arm rests on either side of said base and wherein said core when viewed in front cross-section has the shape of an upwardly opening thick wall channel, and wherein the upper surface of said arm rest and back rest'form a smooth flowing generally circular shape such that the inner side surfaces of the arm rest and back rest walls have a cup shape.
3. The seat member of claim 1 wherein a similarly covered seat cushion of flexible urethane foam is located on the upper surface of said base and wherein supporting legs are attached to said reinforcing element.
References Cited in the file of this patent UNITED STATES PATENTS 2,552,039 Flogaus May a, 1951 2,838,100 Follows June 10', 1958 2,849,058 Bulleri et al. Aug. 26, 1958 2,980,167 Harris et al Apr. is, 1961 2,989,112 Sonnleitner June 20, 1961 3,043,627 Torjusen July 10, 1962 3,083,056 Ward -4 Itiar. 26,1963
FOREIGN PATENTS 5,709,057 Italy July 7, 1958 physicals