Metal working – Upholstered article making – Method
Reexamination Certificate
1999-12-09
2001-09-25
Hughes, S. Thomas (Department: 3726)
Metal working
Upholstered article making
Method
C029S448000, C029S458000, C264S137000, C264S258000, C264S261000, C264S266000, C264S273000, C264S328100
Reexamination Certificate
active
06292990
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of spreading a sheet on a frame-like member such as a core member of a chair seat.
Conventional methods of spreading a square wire mesh on the square frame of a chair are disclosed, for example, in Japanese Examined Utility Model Publication No. Sho54-23523 and Japanese Examined Utility Model Publication No. Sho61-12830.
The former discloses that by inserting a steel wire into each of two opposite sides of a wire mesh, and attaching coil springs having hooks at both ends, with one hook to the steel wire and the other hook to the wire mesh, the wire mesh is spread with a prescribed tension charged against it, by taking advantage of the energizing force of the coil springs.
The latter discloses that a wire mesh is spread by inserting an adapter plate into each of two opposite sides of the wire mesh and then screwing or rivet caulking the adapter plates onto the metal frame while keeping a prescribed tension charged against the wire mesh.
In Japanese Examined Utility Model Publication No. Hei2-9723, it is disclosed that a cushion material made of cloth, having flexibility, is spread and fixed by wrapping the cushion material around the frame and bonding or sewing it to the same.
One of the major problems of a chair formed in accordance with the aforementioned prior arts is that such a chair is not comfortable to sit on because the wire mesh or the like, which is stretched in only two opposite directions, flexes in a limited number of directions.
When the prior arts are applied to products other than a chair (for example, a filter for an air conditioner made by spreading a mesh-like material on a frame member), there are disadvantages, as in the increased time it takes to assemble the larger number of parts, such as hooks and screws, or as in the increased difficulty in making products with an even tension charged against, thus making products of uneven quality.
In relation to a chair, it is described in Japanese Examined Utility Model Publication No. Sho54-6644 and Japanese Examined Patent Publication No. Sho54-20900 that a core member, on which a cloth covering is spread, is fit into a frame-like cover formed out of resin. It is described in Japanese Examined Utility Model Publication No. Sho56-21039 that a core member, on which a cloth covering is spread, is covered with an edge cover formed by extrusion molding of resin. Purportedly, these processes are employed in order to prevent the cloth covering from coming off, as well as, to protect the core member.
However, it takes a lot of time and effort to fit the edge member to a chair. There is also a problem that the edge member is apt to be in an uneven finished state and thus, might come off easily.
SUMMARY OF THE INVENTION
Wherefore, an object of the invention is to provide a method of spreading a sheet on a frame member, which prevents an uneven tension charged against the spread sheet, and by reducing the number of parts necessary for the spreading, enables a more economical sheet spreading process.
Another object of the invention is to provide a method of easily forming a protective member (equivalent to an edge member) for protecting the frame member.
A further object of the invention is to apply the above sheet spreading method and protective member forming method to the seat and the backrest of a chair.
In the sheet spreading method of the invention, placed on a metal mold having a recess corresponding to the shape of a frame member formed therein and a cooling device attached thereto, is a sheet larger than needed for spreading it on the frame member. The sheet is clamped to the metal mold in at least four directions. A molten coating of thermoplastic resin is then formed on the surface of the frame member. When the frame member having the resin coating is fit into the recess of the metal mold with the clamped sheet, part of the resin penetrates the sheet. With cooling device actuated next, the resin coating hardens securing the sheet to the frame member.
The process of spreading a sheet on the frame member is completed when the frame member is released from the clamping and taken out of the metal mold. Since the attached sheet is larger than needed, the excess of the sheet is removed by trimming along the periphery either before or after taking the frame member out of the metal mold.
Since the ultimate tension charged against the spread sheet depends on the shape of the frame member, the ultimate tension is thus controllable by adjusting the frame member's shape.
Therefore, according to the method of the invention, it is possible to spread a sheet on a frame member with an even tension charged against by means of simple structures, such as an aforementioned metal mold and clamps, and of a simple process of forming a coating. Moreover, the metal mold and the clamps are reusable when the shape of the frame member is the same. Therefore, if the present method is employed to spread a sheet on a large number of frame members, the number of necessary elements per frame member can be relatively reduced.
The order of two processes, i.e. clamping a sheet and forming a coating on the frame member, is decided in accordance with the hardenability of the coating because the coating should be molten at least at the time of fitting the frame member into the recess. Specifically, if the coating hardens in a short time, the sheet is clamped first and then the coatings formed on the frame member, which is promptly fit into the recess. If the coating takes time to harden, oppositely, either process may be performed first.
In the sheet spreading method of the invention, the frame member is made of metal, the sheet is a resin mesh or a wire mesh, and the coating is formed by melting and making a powder resin adhere to a preheated frame member.
Although the frame member is preheated in order for the powder resin to melt and adhere, the sheet will not melt when the frame member is pressed into the recess if the sheet is a wire mesh. When polyester, which is heat-resistant up until 230° C., is employed as a resin, the problem of melting the sheet is avoidable so long as the temperature of the frame member is kept below 230° C. (for example 200° C.).
According to the sheet spreading method of the invention, a pre-heated frame member is placed in a flow dipping tank in which powdered resin is suspended in order to make the resin adhere to the frame member. As described, only by placing the frame member in a flow dipping tank, the powder resin melts and adheres to the frame member, and thus the coating is formed making the whole sheet spreading process quite simple.
It is also described in the invention that powder resin is sprinkled in the recess before clamping the sheet on the metal mold. In this case, when the preheated frame member is pressed into the recess, the powder resin melts and penetrates the sheet, and thus, surface treatment of the sheet is performed. Specifically, the part of the sheet surrounding the frame member is covered with an even resin coating, thereby producing an equal finished state of surface treatment to every product.
It is further described in the invention that the thickness of the coating is determined to ensure that by the time of removing the frame member from the metal mold the resin has collected like beading along the border line between the sheet and the frame member. Doing so prevents the sheet from easily coming off on the border line and enables the sheet to be charged with a higher tension.
As aforementioned, according to the sheet spreading method of the invention, it is possible to spread, with an even tension charged against it, a sheet on a frame member. Therefore, if the method is applied to the seat or the backrest of a chair, non-directional flexibility is obtained and thus, such a chair is comfortable to sit on.
When the invention is applied to the seat or the backrest of a chair, a cloth covering may be employed as the sheet or arranged under the wire mesh, enabling the cloth covering also to be spreadable. Further, if the rec
Iseki Toru
Kawashima Takehiko
Aichi Co., Ltd.
Compton Eric
Davis and Bujold, P.L.L.C.
Hughes S. Thomas
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