WO2007115396A1

WO2007115396A1 - Thin-skinned furniture component and method and apparatus for production thereof

Info

Publication number: WO2007115396A1
Application number: PCT/CA2007/000553
Authority: WO
Inventors: Robert W. Germann
Original assignee: Custom Foam Systems Ltd.
Priority date: 2006-04-10
Filing date: 2007-04-03
Publication date: 2007-10-18

Abstract

A moulded product especially suitable as an armrest for a chair exhibits a smooth and wear resistant outer surface and a compressible supporting body portion. The product includes a supporting frame member and the supporting body portion is formed from a gel-like microcellular polyurethane foamable material which encapsulates the frame member. The outer surface is formed from a polyurethane elastomer material having a thickness in the range of about 0.5 mm to 0.9 mm, the polyurethane elastomer material and the gel-like foamable material being bonded together to form an integral body for the product. The invention contemplates apparatus and a method for producing the product.

Description

THIN-SKINNED FURNITURE COMPONENT AND METHOD AND APPARATUS FOR

PRODUCTION THEREOF

The present invention relates to furniture components in general and to a new armrest material in particular.

Background of the invention

Most office chairs are provided with armrests on which the user can rest his or her arms while conducting office-related tasks such as reading or typing. The comfort or feel of the armrest plays a significant role in the comfort level of the worker while the appearance, feel and wear resistance play a significant role in the life of the armrest and the attractiveness or appeal to the potential purchaser. From the standpoint of the manufacturer it is important that the office chair be comfortable and appealing to the customer and it is also important that the cost of the chair components be as inexpensive as possible while providing all of the desirable qualities that will appeal to the customer so that the manufacturer can provide a product that will fulfill the customer's needs and desires while providing a suitable level of profit.

With the recent emphasis on ergonomic correctness in the workplace, in view of keyboarding-related physical problems such as carpal tunnel syndrome and neck and shoulder injuries, it is important that the office chair provide adequate support for the worker's body and extremities. When it comes to the armrest portion of an office chair it is desirable that the armrest provide a degree of compression when the arm or elbow is resting thereon, without being so soft that the worker can feel the underlying support structure. On the other hand, the armrest should not be so hard that it is little different from a piece of wood covered with a thin fabric cover, providing little or no comfort to the user. Additionally, the customer of an office chair will be looking for wear and cut resistance, such that he or she will be confident that the chair will last a long time without requiring repair or replacement of the armrest, given that the armrests will be in use at least 50% of the time that a person is sitting in the chair. The applicant herein, Custom Foam Systems (hereinafter CFS) has developed several products which are in commercial use in various products running from tractor seats to office chair armrests, which products satisfy many of the criteria established by their customers. While such products are excellent and find considerable acceptance, they do have some drawbacks from the standpoint of cost and thus there is room to improve the products. Those existing products are described below.

TUFFSKIN™ is a two component product that is used to make tractor seats. It utilizes an outer skin of an elastomer material that is first of all sprayed into a suitable mould to a thickness in the order of 1 mm (typically from about 0.9 mm to about 1.5 mm). The elastomer used is a special polyurethane material co-developed by CFS and Bayer Material Science, which material increases the physical properties of standard polyurethane elastomers at thinner cross-sections than typically processed. The TUFFSKIN™ product also utilizes a polyurethane foam material that is blown into the mould once the skin material has been sprayed onto the surface of the mould and the mould has been closed. The foam is injected using water as the blowing agent. The elastomer skin and the blown foam create a chemical bond as the materials cure within the mould. The resulting part has an elastomeric outer skin which typically has a black textured surface and it has a flexible foam supporting body, shaped to the desired profile of the seat. In comparison to traditional products made from self-skinning foams the TUFFSKIN™ product exhibits an outer thin skin that has a density of about 60 pounds per cubic foot (pcf) and a core or support with a density of about 3.5 pcf. The traditional product, where the outer skin forms autonomously on the foam, has an even thinner skin but it has a consistent density of about 25 pcf throughout. The TUFFSKIN™ product exhibits better abrasion, mare and cut resistance and tear strength with much less compression.

During the development of the TUFFSKIN™ product it was determined that for the benefits of the material combination of elastomer skin and flexible foam core to be realized, the elastomer skin had to be highly consistent and thin to yield an attractive result. If the spray skin "pooled" or varied or was overall too thick, the resulting part would feel too hard or the pooling would be noticeable to the touch. The consistency of the skin thickness is also a critical element in maximizing the durability of the product. Any significant transition from thick to thin creates a "hinge point" where under repeated compressions there can be premature failure of the product. CFS has been able to automate the production of TUFFSKIN™ products, such that the polyurethane elastomer for the skin is sprayed robotically into the moulds, whereby skin thickness can be closely controlled. As indicated, this product finds particular use in tractor seats, although if a thicker skin is provided the product can be shaped and moulded for other high-usage products. Another CFS product that finds particular acceptance in the office furniture business is their GELFOAM™ product, again co-developed with Bayer Material Science. GELFOAM™ is a variation of microcellular polyurethane which possesses the surface characteristics of self-skinning or integral skin foam, except that when squeezed or compressed by hand and released it reacts like a conventional gel material but with its own distinguishing recovery cycle and feel. GELFOAM™ was also formulated to ensure that the finished moulded product has physical properties consistent with self-skinning foam. Physical properties necessary to be serviceable for armrest applications include abrasion resistance, mare resistance and elongation. This product was developed to gain market share in applications where gel products were growing, as for example in computer keyboard wrist rests, office chair armrests and stress relieving novelty items such a squeeze-balls. In accelerated field use tests GELFOAM™ products performed consistently well when compared to other self-skinning materials but did not perform as well as most PVC skin products.

While the above-mentioned products all have their positive attributes there is still a need for new product that will provide the wear resistance and feel of the TUFFSKIN™ product with the feel and comfort of the GELFOAM™ product while not increasing costs to the furniture manufacturer.

Summary of the Invention

The needs established by the furniture manufacturers have been met with the product of the present invention, namely a two-component material that is particularly suitable for use as an armrest on an office chair that provides excellent wear resistance, as well as excellent appearance and feel at a reasonable cost to the furniture manufacturer. The material of the invention includes a polyurethane elastomer material that is sprayed onto the internal surface of a mould as a consistent and uniform thin layer over what will be the operating surface of an armrest. When the mould is closed a self-skinning gel-like microcellular polyurethane material such as GELFOAM™ is injected into the mould to fill the mould to a desired level. The two materials will bond together as the materials cure within the mould, and when the resulting moulded product is removed from the mould it will exhibit all of the desirable traits that the furniture manufacture is seeking. The outer skin has the desired, preferably textured, appearance while exhibiting excellent abrasion resistance, mare resistance and elongation, while the body of the product exhibits the desired compression resistance and recovery characteristics that appeal to the ultimate user of an armrest, the office worker.

In order to economically manufacture armrests, or any other products requiring similar characteristics, it was necessary to devise apparatus that would sequentially attend to the various stages in the production of product. Thus, the present invention also contemplates apparatus for manufacturing appropriate product, including armrests for office chairs. The apparatus of this invention contemplates a 10-station carousel, with each station comprising an independent pneumatically-operated mould press. A 10-station operation was considered to be optimum on the basis of the cure time of 5 minutes. With each of the operation process steps taking approximately one minute, including the robot spraying of the elastomer skin material, and there being four other operation steps involved, a 10-station operation turned out to be most effective and efficient. In summary, therefore, the present invention is seen to contemplate a moulded product exhibiting a smooth and wear resistant outer surface and a compressible supporting body portion, the product comprising: a supporting frame member; the supporting body portion being formed from a gel-like microcellular polyurethane foamable material and encapsulating the frame member; and the outer surface being formed from a polyurethane elastomer material having a thickness in the range of about 0.5 mm to 0.9 mm, the polyurethane elastomer material and the gel-like foamable material being bonded together to form an integral body for the product. The present invention also contemplates a method for producing a moulded product utilizing a mould including first and second mating sections that can be opened and closed relative to each other and which define a cavity profiled to the shape of such product, comprising the steps of: spraying a release agent onto an interior surface of at least the first mould section; spraying a thin layer of a polyurethane elastomer onto the release agent; removing any overspray of polyurethane elastomer from the first mould section; inserting a supporting frame member for the product into the first mould section; closing the first and second mould sections and injecting into the mould cavity defined by the mould sections a gel-like self-skinning microcellular polyurethane foamable material; permitting the foamable material to expand and fill the mould cavity and to bond to the polyurethane elastomer as the polyurethane elastomer and the foamable material cure within the mould cavity; and removing the moulded product from the mould following the curing of the polyurethane elastomer and the foamable material.

Finally, it is seen that the present inventions contemplates apparatus for producing a moulded product, the apparatus comprising: a carousel defining a plurality of circumferentially spaced moulds at the outer periphery thereof, each such mould including first and second mating sections that can be opened and closed relative to each other and which define a cavity profiled to the shape of the product; a plurality of operation stations spaced apart around the carousel; means for rotating the carousel to present each mould respectively and in timed sequence to the operating stations seriatim; a first station including first spraying means for spraying a release agent onto an interior surface of at least the first mould section present at the first station; a second station including second spraying means for spraying a polyurethane elastomer onto the release agent; a third station including means for removing any overspray of the polyurethane elastomer from the first mould section; means at third station for inserting a supporting frame member into the first mould section; a fourth station including means for closing the first and second mould sections and for injecting a gel- like self-skinning microcellular polyurethane foamable material into the cavity defined by the mould sections; a plurality of subsequent stations at which curing of the polyurethane elastomer and the foamable material takes place; and a final station at which the first and second mould sections are opened and a finished product is removed from the mould.

Brief Description of the Drawings

The invention will now be described more fully and with reference to the drawings wherein:

Figure 1 is a cross-sectional view of a typical armrest for an office chair incorporating the material combination of the present invention;

Figure 2 is a flow chart indicating the steps involved in the process of the present invention; and

Figure 3 is a schematic representation of the apparatus which is effective in carrying out the process of the present invention.

Description of the Preferred Embodiment

The present invention incorporates many, if not all, of the advantageous aspects of the TUFFSKIN™ and the GELFOAM™ products already manufactured by CFS. Surprisingly, it has been discovered that the gel-like foam material used in the single component GELFOAM™ product, which material is of the self-skinning variety, is compatible with the polyurethane elastomer used as the skin material in the two- component TUFFSKIN™ product. When the gel-like foam material is brought into contact with the polyurethane elastomer there is a bonding between the two materials as they cure, with the result being a supporting body of the gel-like foam material covered by a thin skin of the polyurethane elastomer. The skin of the ensuing product exhibits all of the desirable qualities indicated above, while the supporting material exhibits the desirable qualities of the GELFOAM™ product, also as indicated above. When the ensuing product is an armrest for an office chair the product becomes highly desirable for the furniture manufacturer, as it provides optimum comfort, with excellent wear resistance, mare resistance, cut resistance, abrasion resistance and elongation. It has also been ascertained that it is possible to decrease the skin thickness typically associated with the TUFFSKIN™ product without decreasing the desirable properties of the skin, thereby reducing manufacturing costs.

Figure 1 is illustrative of a typical armrest utilizing the principles of the present invention. The armrest 10 is shown in transverse cress-section, whereby it includes a frame member 12 that is typically of a plastic material, although it could also be formed of aluminum, wood, or any other supporting material. The frame member 12 will provide stability to the armrest after moulding and it will also serve as an anchor for the armrest when it is assembled to a suitable supporting frame of the office chair.

After moulding is complete the formed armrest 10 will also exhibit the supporting material 14 which is formed to the desired shape of the armrest, and which also is moulded about the frame member 12 so as to fix the frame member in place within the armrest 10. The material 14 starts as a gel-like foamable self-skinning microcellular polyurethane material such as GELFOAM™ currently available from CFS. A self-skinning material is one which, as it cures, forms a thin skin on its exterior surface. The exterior skin of such a material will often be acceptable as the exterior surface of a product and such material is not usually associated with other exterior materials since such exterior materials are not required for applications in which such gel-like material is used.

The armrest 10 of the present invention also incorporates an exterior surface or layer 16 formed from a polyurethane elastomer that is moulded along with the gel-like foam material in a mould press. The polyurethane elastomer is sprayed onto the appropriate surface of the mould before the gel-like foam material is injected into the mould, such that the polyurethane elastomer and the gel-like foam material will bond together as they cure. The moulded armrest will thus exhibit the properties or characteristics of a gel-like foam material with an attractive outer surface formed by the polyurethane elastomer, achieving all of the desirable characteristics of the TUFFSKIN™ and GELFOAM™ products at a reasonable manufacturing cost, making for a very attractive product for the furniture manufacturer. The mould surface will preferably be etched so that the exterior surface of the layer 16 will exhibit a generally textured appearance, which is appealing to most customers.

Figure 2 illustrates a flow chart which sets forth the method of the present invention, in association with Figure 3 which illustrates schematically the apparatus especially adapted to produce the product of the present invention. As shown, the method and the apparatus comprise a plurality of steps accomplished at an equivalent plurality of operation stations, each adapted to perform a specific operation, although five of the stations are utilized for the curing of the polymeric materials forming the product.

The method of the invention starts with step 50, the spraying of a mould release agent 100 onto the operative surfaces of an open mould 200 at the first station 300, the mould cavity reflecting the final shape of the product to be moulded therein. The mould 200 includes first and second mould sections 202 and 204. The mould section 202 is fixed to a carousel 206 that rotates in a timed fashion to bring each mould seriatim to each operation station. The second mould section 204 travels with the first mould section and is movable relative thereto so as to open and close the mould itself as desired. Each mould section has a portion of the product profile or shape formed therein such that the mould cavity is defined by the mould sections when the mould is closed. The second step 52 involves the optional spraying of a thin film of an appropriate colouring agent, such as paint 102 onto the release agent in the mould 200, also at the first station 300. The third step 54 involves the robotic spraying, by way of a robot 302, of the polyurethane elastomer 104 that will form the skin 16 of the product, into the mould 200 at the second station 304. With the robotic spraying of the elastomer into the mould 200 it is possible to carefully control the thickness of the material such that the thickness of the skin 16 will be in the range of from about 0.5 mm to about 0.9 mm, much less than that of the TUFFSKIN™ product. The fourth step 56 involves scraping any overspray of the polyurethane elastomer from the mould along the parting line 18 of the skin 16 as shown in Figure 1. This step takes place at the third station 306 and will ensure that there is a clean line where the skin 16 meets the material of the supporting body 14. The fifth step 58 also takes place at the third station 306 and involves positioning the frame member 12 into the mould cavity 200. The frame member will be supported by appropriate supports within the cavity so that the gel-like material can flow around the frame member and thus fix it in place within the final product.

The sixth step 60 takes place at the fourth station 308 where the mould sections 202, 204 are brought together to close the mould, so that the mould cavity will enclose the final form of the product to be moulded therein. At the fourth station 308 the gel- like self-skinning microcellular polyurethane foam material 106 is injected into the mould cavity. The fifth through ninth stations 310-318 involve the curing step 62 of the polyurethane elastomer and the gel-like foam material as they bond together and form around the frame member 12 to result in the desired final product. The seventh and last step 64 takes place at the tenth station 320 where the first and second mould sections 202, 204 are separated to open the mould 200 so that the final product 10 can be removed therefrom.

The foregoing has described the preferred aspects of the present invention although it is understood that a skilled individual in the art could vary certain details of the invention without departing from the spirit thereof.

Claims

CLAIMS:

1. A moulded product exhibiting a smooth and wear resistant outer surface and a compressible supporting body portion, said product comprising: a supporting frame member; said supporting body portion being formed from a gel-like microcellular polyurethane foamable material and encapsulating said frame member; and said outer surface being formed from a polyurethane elastomer material having a thickness in the range of about 0.5 mm to 0.9 mm, said polyurethane elastomer material and said gel- like foamable material being bonded together to form an integral body for said product.

2. A method for producing a moulded product utilizing a mould including first and second mating sections that can be opened and closed relative to each other and which define a cavity profiled to the shape of such product, comprising the steps of:

- spraying a release agent onto an interior surface of at least said first mould section; - spraying a thin layer of a polyurethane elastomer onto said release agent;

- removing any overspray of said polyurethane elastomer from said first mould section;

- inserting a supporting frame member for said product into said first mould section; - closing said first and second mould sections and injecting into said mould cavity defined by said mould sections a gel-like self-skinning microcellular polyurethane foamable material;

- permitting said foamable material to expand and fill said mould cavity and to bond to said polyurethane elastomer as said polyurethane elastomer and said foamable material cure within said mould cavity; and

- removing said moulded product from said mould following the curing of said polyurethane elastomer and said foamable material.

3. The method of claim 2 including the steps of: - spraying a layer of colouring agent onto said release agent and spraying said thin layer of a polyurethane elastomer onto said colouring agent;

4. Apparatus for producing a moulded product, said apparatus comprising:

- a carousel defining a plurality of circumferentially spaced moulds at the outer periphery of said carousel, each such mould including first and second mating sections that can be opened and closed relative to each other and which define a cavity profiled to the shape of said product;

- a plurality of operation stations spaced apart around said carousel; - means for rotating said carousel to present each mould respectively and in timed sequence to said operating stations seriatim;

- a first said station including first spraying means for spraying a release agent onto an interior surface of at least said first mould section present at said first station; - a second said station including second spraying means for spraying a polyurethane elastomer onto said release agent;

- a third said station including means for removing any overspray of said polyurethane elastomer from said first mould section;

- means at said third station for inserting a supporting frame member into said first mould section;

- a fourth said station including means for closing said first and second mould sections and for injecting a gel-like self-skinning microcellular polyurethane foamable material into said cavity defined by said mould sections;

- a plurality of subsequent stations at which curing of said polyurethane elastomer and said foamable material takes place; and

- a final station at which said first and second mould sections are opened and a finished product is removed from said mould.

5. The apparatus of claim 4 including third spraying means at said first station for spraying a colouring agent onto said release agent, said second spraying means at said second station then spraying said polyurethane elastomer onto said colouring agent.