HEIGHT ADJUSTABLE DESK AND CHAIR Technical Field The present invention relates, in general, to desks and chairs for use in classrooms of a variety of schools, for example, primary schools, middle schools, and high schools, so as to be used by students and, more particularly, to a height adjustable frame for such desks and chairs, of which the legs each have a height adjustable telescopic structure so as to allow a user to adjust the height of a desk or a chair, as desired. Each of the telescopic legs of the height adjustable frame includes an outside pipe having a plurality of height adjusting holes on its sidewall along an axial direction. An inside pipe, having an outer diameter not larger than an inner diameter of the outside pipe and a button holding hole at a predetermined position of its sidewall, is axially fitted into the outside pipe so as to form the height adjustable telescopic leg. A spring is installed in the inside pipe such that an end of the spring is positioned around the button holding hole of the inside pipe, and a locking button is mounted to the end of the spring so as to be set in the button holding hole of the inside pipe. The locking button has a locking groove around its external surface, and is inserted into a selected one of the height adjusting holes of the outside pipe so as to lock the inside and outside pipes together in a height-adjusted position. In such a case, the button holding hole of the inside pipe engages at an edge thereof with the locking groove of the locking button, thus preventing the locking button from being undesirably retracted backward from the selected one of the height adjusting holes.

Background Art Conventional height adjustable frames for desks and chairs are typically classified into the following two types. In a first-type height adjustable frame for desks and chairs, the legs each comprise an outside pipe and an inside pipe

which are assembled into a height adjustable telescopic structure. The outside pipe and the inside pipe are made of a material except for a metal, and are assembled together into the telescopic structure such that the inside pipe is axially fitted into the outside pipe. In the above first-type frame, the length of each leg is adjusted by controlling an overlapping length of the inside pipe relative to the outside pipe, as desired, prior to tightening the inside and outside pipes to each other to frictionally fix the inside pipe to the outside pipe in a height-adjusted position. In a second-type height adjustable frame for desks and chairs, the legs each comprise an outside pipe and an inside pipe which are assembled into a height adjustable telescopic structure. In the above second-type frame, the length of each leg is adjusted by controlling an overlapping length of the inside pipe relative to the outside pipe, as desired, prior to fixing the inside pipe to the outside pipe in a height-adjusted position by setting a fixing pin or a setscrew in aligned holes of the inside and outside pipes.

However, the first-type height adjustable frame is problematic in that the junction of the inside and outside pipes of the legs becomes worn and the properties of the material of the legs are changed, according to a repeated height adjustment of the legs over a lengthy period of time, so that the junction loses desired friction and the operational reliability of the frame is degraded. The second-type height adjustable frame is problematic in that the gap between the holes of the inside and outside pipes and the fixing pin or the setscrew becomes wide, according to a repeated height adjustment of the legs over a lengthy period of time, so that it is necessary to use an additional piece to compensate for the widened gap. Therefore, the maintenance cost of the second-type height adjustable frame is increased.

Furthermore, the first-type height adjustable frame undesirably forces a user to repeatedly control the overlapping length of the inside and outside pipes and tighten the two pipes to each other to frictionally fix the adjusted length of the legs. The second-type height adjustable frame also forces a user to repeatedly control the overlapping length of the inside and outside pipes while aligning

desired holes of the two pipes, and set the pin or the setscrew to the aligned holes of the two pipes. Therefore, the first-and second-type height adjustable frames are inconvenient to use.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a height adjustable frame for desks and chairs, of which the legs each have a height adjustable telescopic structure so as to allow a user to easily adjust the height of a desk or a chair, as desired, by retracting a locking button of an inside pipe backward from one of height adjusting holes of an outside pipe so as to allow the locking button to be elastically inserted into another one of the height adjusting holes, thus locking the inside pipe to the outside pipe in a height- adjusted position.

In the height adjustable frame of the present invention, the locking button of the inside pipe has a locking groove around its external surface and a stop flange at its inside end. The stop flange prevents an outward removal of the locking button from the leg, and the locking groove prevents an undesired retraction of the locking button from a selected one of the height adjusting holes.

Each of the telescopic legs of the height adjustable frame includes the outside pipe having the height adjusting holes on its sidewall. The inside pipe, having a button holding hole on its sidewall, is axially fitted into the outside pipe so as to form the height adjustable telescopic leg. The spring is installed in the inside pipe, and the locking button is mounted to an end of the spring so as to be set in the button holding hole of the inside pipe. When the locking button is retracted from one of the height adjusting holes of the outside pipe by a user, the locking button may be elastically inserted into another one of the height adjusting holes, so that the user can easily adjust the height of a desk or a chair, without fearing loss of the locking button. Due to the locking groove of the locking

button, it is possible to prevent the locking button from being undesirably retracted backward from a selected one of the height adjusting holes.

The height adjustable frame for desks and chairs of the present invention is advantageous in that it is easy and simple to adjust the height of the frame within a short period of time, without losing a fastening element. In addition, due to the locking groove, the locking button is prevented from being undesirably retracted, so that the height-adjusted position of the frame is reliably maintained.

The height adjustable frame of the present invention also prevents a desk or a chair from being undesirably reduced in its height or collapsed, so that the user can be protected from injury.

Brief Description of the Drawings The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is an exploded perspective view of a leg of a height adjustable frame for desks and chairs, according to a preferred embodiment of the present invention; Fig. 2a is a sectional view of the leg of Fig. 1 when a spring-biased button of an inside pipe of the leg is pushed outward by a spring into a selected one of height adjusting holes of an outside pipe so as to lock the inside pipe to the outside pipe at a height-adjusted position; Fig. 2b is a sectional view of the leg of Fig. 1 when the inside pipe is lifted slightly up relative to the outside pipe so as to align a button holding hole of the inside pipe with the selected one of the height adjusting holes and thereby allow the spring-biased button to be moved in the two aligned holes; Fig. 2c is a sectional view of the leg of Fig. 1 when the spring-biased button is retracted backward to be completely released from the selected one of the height adjusting holes so as to allow a user to adjust the height of the leg, as

desired; and Fig. 3 is a perspective view of a desk having the height adjustable frame according to the present invention.

Best Mode for Carrying Out the Invention Reference should now be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.

As shown in the Figs. 1 to 3, a height adjustable frame for desks and chairs according to a preferred embodiment of the present invention is used in a manner that it is mounted to an upper panel of a desk 9 or a seat of a chair (not shown) so as to support the upper panel or the seat. The height adjustable frame includes a plurality of telescopic legs having a height adjustable structure. Each of the telescopic legs of the height adjustable frame comprises an outside pipe 1 forming a lower pipe of the leg, with a plurality of height adjusting holes 3 formed along a sidewall of the outside pipe 1. The telescopic leg also has an inside pipe 2 which forms an upper pipe of the leg and has an outer diameter not larger than an inner diameter of the outside pipe 1. The inside pipe 2 is axially fitted into the outside pipe 1 so as to be extended from or retracted into the outside pipe 1, as desired. A button holding hole 3'is formed at a predetermined position of a sidewall of the inside pipe 2. A U-shaped spring 4 acting as a biasing member is installed in the inside pipe 2.

A first end of the U-shaped spring 4 is slightly bent outward and is leaned against an inner surface of the inside pipe 2, so that the first end of the spring 4 is less likely to undesirably move on the inner surface of the inside pipe 2. A second end 5 of the spring 4 is bent outward at an angle of about 90° so as to be positioned around the button holding hole 3'of the inside pipe 2. A locking button 6 is mounted to the bent second end 5 of the U-shaped spring 4, and is set in the button holding hole 3'of the inside pipe 2. The locking button

6 has a locking groove 7 formed around an external surface of the button 6, and a stop flange 8 formed at an inside end of the button 6. The locking button 6 is always biased outward by the spring 4, so that the button 6 may be removed outward from the button holding hole 3'of the inside pipe 2 and one of the height adjusting holes 3 of the outside pipe 1. However, the inside pipe 2 stops the stop flange 8 of the locking button 6, thus preventing an outward removal of the locking button 6 from the leg. In addition, the button holding hole 3'of the inside pipe 2 engages at an edge thereof with the locking groove 7 of the locking button 6 due to weight of the inside pipe 2 once the inside pipe 2 is locked to the outside pipe 1 at a height-adjusted position, so that the locking button 6 is prevented from being undesirably retracted backward from a selected one of the height adjusting holes 3. Therefore, the height-adjusted position of the legs is stably maintained.

Industrial Applicability As described above, the present invention provides a height adjustable frame for desks and chairs. In the frame, the legs each have a height adjustable telescopic structure so as to allow a user to adjust the height of a desk or a chair, as desired. Each of the telescopic legs of the height adjustable frame includes an outside pipe having a plurality of height adjusting holes on its sidewall. An inside pipe, having a button holding hole at a predetermined position of its sidewall, is axially fitted into the outside pipe so as to form the height adjustable telescopic leg. A spring is installed in the inside pipe such that an end of the spring is positioned around the button holding hole of the inside pipe, and a locking button is mounted to the end of the spring so as to be set in the button holding hole of the inside pipe. In order to adjust the height of the desk or the chair, the spring-biased locking button is retracted backward to allow a user to control the length of the overlapping junction of the inside and outside pipes.

The locking button is, thereafter, elastically inserted into a selected one of the

height adjusting holes, so that the inside and outside pipes are locked together in a height-adjusted position.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.