Backrest and method for making backrest

Abstract

A backrest includes a frame, a web and a ring. The frame includes a margin and two rims extending on a side of the margin and a gap defined between the rims. The web is spread on the side of the frame. The ring is put on the web and fit in the annular groove so that the web is tightly spread on the frame.

Description

FIELD OF INVENTION

The present invention relates to a backrest and, more particularly, to a method for making such a backrest.

BACKGROUND OF INVENTION

A typical chair for use in an office includes a seat and a backrest. The seat and the backrest are both made from foam material so as to provide a soft feeling to a person sitting in the chair. However, the backrest made of foam material is not good for dissipating heat produced by the person. Moreover, the backrest made of foam material is heavy and bulky and, hence, not economic regarding transportation.

The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.

SUMMARY OF INVENTION

It is an objective of the present invention to provide a backrest with good dissipation of heat produced by a person's back laid against it.

It is another objective of the present invention to provide a backrest that is light in weight and compact in size.

According to the present invention, a backrest includes a frame, a web and a ring. The frame includes a margin and two rims extending on a side of the margin and a gap defined between the rims. The web is spread on the side of the frame. The ring is put on the web and fit in the annular groove so that the web is tightly spread on the frame.

Other objects, advantages and novel features of the invention will become more apparent from the following detailed description in conjunction with the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described via detailed illustration of embodiments referring to the drawings.

FIG. 1 is a flowchart of a method for making a backrest according to the preferred embodiment of the present invention.

FIG. 2 is an exploded view of a backrest according to the preferred embodiment of the present invention.

FIG. 3 is a cross-sectional view of the backrest of FIG. 2.

FIGS. 4-9 are perspective views of a mold assembly in various steps of the method of FIG. 1 for making the backrest of FIG. 2.

FIG. 10 is a perspective view of the backrest of FIG. 1.

FIG. 11 is a perspective view of the backrest of FIG. 10 used in a chair.

DETAILED DESCRIPTION OF EMBODIMENTS

In accordance with the preferred embodiment of the present invention, a backrest shown in FIGS. 2, 3, 10 and 11 is made in a method shown in FIGS. 1 and 4-9.

Referring to FIG. 2, the backrest includes a frame 10, a web 20, a ring 30, a cushion 40 and a cover 50. The frame 10 includes a margin 11 and two rims 12 extending on a front side of the margin 11. A gap 13 is defined between the rims 12.

Referring to FIG. 3, the web 20 is put on a front side of the frame 10. The ring 30 is put on a front side of the web 20. The ring 30 and an annular portion of the web 20 are fit into the annular groove 13. Thus, the web 20 is tightly spread on the frame 10, i.e., tension is produced in the web 20. The cushion 40 is put in the frame 10. The cushion 40 is compressed between the margin 11 and the web 20. Thus, the web 20 is more tightly spread on the frame 10, i.e., the tension in the web 20 is increased. The cover 50 is installed around the frame 10.

Referring to FIGS. 1 and 4, at step S10, a mold assembly is provided. The mold assembly includes a lower mold 60, a middle mold 62 and an upper mold 70. The lower mold 60 defines a cavity 61 in an upper side. The profile of the cavity 61 is compliant with that of the backrest. The profile of the middle mold 62 is compliant with that of the cavity 61.

The upper mold 70 defines a cavity 71 in a lower side. The profile of the cavity 71 is compliant with that of the middle mold 62.

Referring to FIGS. 1 and 5, at step S15, the frame 10 is put in the cavity 61. The rims 12 face up.

Referring to FIGS. 1 and 6, at step S20, the middle mold 62 is lowered against the margin 11. Thus, the frame 10 is held in position. The rims 12 are exposed.

Referring to FIGS. 1 and 7, at step S25, the web 20 is laid on the middle mold 62. The web 20 covers the rims 12.

Referring to FIGS. 1 and 8, at step S30, the ring 30 is put on the web 20. The ring 30 and an annular portion of the web 20 are forced into the annular groove 13. Thus, the web 20 is tightly spread on the frame 10.

Referring to FIGS. 1 and 9, at step S35, the upper mold 70 is lowered against the ring 30. High frequency is exerted on the frame 10, the web 20 and the ring 30. Thus, the frame 10, the web 20 and the ring 30 are heated and therefore partly melted. The frame 10, the web 20 and the ring 30 adhere to one another when they cool down.

Referring to FIG. 1, at step S40, the upper mold 70 is lifted from the ring 30 and returned to its original position. The middle mold 62 is lifted from the lower mold 60 and returned to its original position.

At step S45, the frame 10, the web 20 and the ring 30, as a whole, are moved from the middle mold 62.

At step S50, the cushion 40 is put in the frame 10. The cushion 40 is compressed between the margin 11 and the web 20. Thus, the web 20 is more tightly spread on the frame 10.

At step S55, the cover 50 is installed around the frame 10.

At step S60, the backrest is finished.

The present invention has been described via detailed illustration of some embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.

Claims

1. A backrest including:

a frame including a margin and two rims extending on a side of the margin and a gap defined between the rims;

a web spread on the side of the frame; and

a ring put on the web and fit in the annular groove so that the web is tightly spread on the frame.

2. The backrest according to claim 1 including a cushion arranged between the margin and the web so that the web is more tightly spread on the frame.

3. The backrest according to claim 1 including a cover installed around the frame.

4. A method for making a backrest comprising the following steps:

providing a frame including a margin and two rims extending on a side of the margin and a gap defined between the rims;

providing a web;

providing a ring;

providing a mold assembly including: a lower mold defining a cavity in an upper side; a middle mold; and an upper mold defining a cavity in a lower side;

putting the frame in the cavity of the lower mold with the rims facing up;

holding the frame in position by means of lowering the middle mold against the margin, with the rims exposed.

spreading the web on the middle mold, with the web covering the rims;

forcing the ring and an annular portion of the web into the annular groove so as to tightly spread the web on the frame;

pressing the ring, the web and the frame against one another by means of lowering the upper mold against the ring; and

adhering the frame, the web and the ring to one another;

returning the upper mold and the lower mold to their original positions; and

removing the frame, the web and the ring, as a whole, from the middle mold.

5. The method according to claim 4 wherein the step of adhering the frame, the web and the heat pressing the ring to one another includes a step of partly melting them.

6. The method according to claim 5 wherein the step of partly melting the frame, the web and the ring includes a step of heating them.

7. The method according to claim 6 wherein the step of heating the frame, the web and the ring includes a step of exerting high frequency on them.

8. The method according to claim 4 including a step of providing a cushion between the margin and the web so that the web is more tightly spread on the frame.

9. The method according to claim 4 including a step of providing a cover around the frame.