WO2002044881A1

WO2002044881A1 - Portable keyboard

Info

Publication number: WO2002044881A1
Application number: PCT/KR2001/001991
Authority: WO
Inventors: Kyung-Il Baek
Original assignee: Oh, Soon-Bong
Priority date: 2000-11-30
Filing date: 2001-11-21
Publication date: 2002-06-06
Also published as: KR20020042290A; AU2002218541A1

Abstract

Disclosed is a portable keyboard. At least four main frames, which are arranged along a transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are paralled one to another, with each hinge shaft extending in a longitudinal direction. At least one auxillary frame is foldably connected with one of the four main frames by a pair of hinge shafts which extend in the transverse direction. Each of the four main frames includes a key section having one or more keys. A connector is mounted to one of the four main frames or the auxillary frame. Support means for supporting a portable information terminal is installed on the auxillary frame. The auxillary frame includes locking means for locking the main frames and the auxillary frame to each other in a folded status.

Description

PORTABLE KEYBOARD

Technical Field

The present invention relates to a keyboard, and more particularly, the present invention relates to a portable keyboard which can be folded into a pocket size to be easily carried along with a portable information terminal such as a personal digital assistant (PDA) , a radiotelephone and the like, and can be unfolded upon use to serve as a normally sized conventional keyboard, whereby portability is secured due to slimness and a small size upon folding of the keyboard.

Background Art

A typical example of a foldable keyboard capable of being folded and unfolded is disclosed in U.S. Patent No. 6,174,097. This foldable keyboard has a drawback in that, since a conventional keyboard structure which is applied to a notebook computer, etc. is modified in such a way as to be folded and unfolded, its volume and weight cannot but be fairly large, whereby it is inconvenient to carry the keyboard in a folded status, and thereby portability is deteriorated. Also, because keys are arranged in the form of cells which are separated one from another, and slide and link mechanisms should be provided to enable upward and downward movements of the keys, the keyboard structure is complicated, whereby a manufacturing cost is increased and an economical burden is imposed on a user.

Further, due to the fact that a connector of the foldable keyboard has only one fixed shape, the foldable keyboard is not compatible with various portable information terminals such as a PDA, a radiotelephone and the like, which have connectors of other shapes. Thus, since it is necessary to newly purchase a keyboard depending upon a type of a portable information terminal, troublesomeness and inconvenience are caused.

Disclosure of the Invention

Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a portable keyboard which can be folded and unfolded as an input device for a portable information terminal or a desktop computer, occupies a reduced volume and has a small thickness in a folded status so as to decrease an entire weight of the portable keyboard, can serve in an unfolded status as a normally sized conventional keyboard, and has a simple construction and operational accuracy in such a way as to reduce a manufacturing cost and secure operational reliability.

Another object of the present invention is to provide a portable keyboard which accomplishes compatibility of a connector with respect to various portable information terminals having connectors differently shaped depending upon a manufacturer or a model . In order to achieve the above object, according to one aspect of the present invention, there is provided a portable keyboard characterized in that at least four main frames, which are arranged along a transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in a longitudinal direction; at least one auxiliary frame is foldably connected with one of the four main frames by a pair of hinge shafts which extend in the transverse direction; each of the four main frames includes a key section having one or more keys; a connector is mounted to one of the four main frames or the auxiliary frame; support means for supporting a portable information terminal is installed on the auxiliary frame; and the auxiliary frame includes locking means for locking the main frames and the auxiliary frame to each other in a folded status.

According to another aspect of the present invention, five main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction.

According to another aspect of the present invention, four main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction.

According to another aspect of the present invention, five main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction; and one auxiliary frame is foldably connected with a second main frame by the pair of hinge shafts which extend in the transverse direction.

According to another aspect of the present invention, the five main frames and one auxiliary frame are connected one with another by the respective pairs of hinge shafts which extend in the longitudinal and transverse directions, in a manner such that they can be folded inward onto another frame. According to another aspect of the present invention, four main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction; and two auxiliary frames are foldably connected with a first main frame by two pairs of hinge shafts which extend in the transverse direction.

According to another aspect of the present invention, the support means is composed of first and second auxiliary frames, the connector is integrally mounted to a lower part on an inner surface of the first auxiliary frame, marginal portions are respectively formed at one ends of first and fourth main frames of which side walls respectively delimit lower and upper cases, and the marginal portion of the fourth main frame is defined with an accommodating groove in which the connector of the first auxiliary frame can be accommodated.

According to another aspect of the present invention, a key, which is positioned on at least one folding line between two adjoining main frames, is divided into at least two key portions so that the two key portions can be folded along the folding line and operated as one key upon being unfolded.

According to another aspect of the present invention, the auxiliary frame includes an infrared beam maintaining arch which has at an upper part thereof an infrared optical element and which possesses a support plate capable of being moved in an interlocked manner therewith, and the infrared optical element is arranged in a manner such that it can be maintained at a predetermined angle by the infrared beam maintaining arch.

According to another aspect of the present invention, the support plate is defined at both sides thereof with a pair of engaging grooves in a manner such that movement of the holder pate can be limited by a pair of resilient bars formed on inner edges of the infrared beam maintaining arch and a pair of engaging projections formed on the pair of resilient bars to be engaged into the pair of engaging grooves, and the infrared beam maintaining arch is elastically biased by an arch spring toward its original position.

According to another aspect of the present invention, the key section of the main frame comprises a contact connection circuit board which is positioned on a bottom surface of the main frame and has a plurality of contacts; a rubber keypad which is positioned on the contact connection circuit board and has a plurality of rubber keys corresponding to the contacts; an attachment plate which is defined with a plurality of rubber key insertion holes corresponding to the rubber keys so that the rubber keys of the rubber keypad can project upward through the rubber key insertion holes; and a hard cap which is bonded to upper ends of the rubber keys projecting upward through the rubber key insertion holes of the attachment plate.

According to still another aspect of the present invention, the locking means is configured in a manner such that a pair of folded status maintaining protrusions are formed on upper ends of both side walls of the auxiliary frame, and the main frames and the auxiliary frame are locked to each other in the folded status. According to yet still another aspect of the present invention, the locking means is configured in a manner such that a pair of engaging prominences are formed on an outer surface of a finally folded main frame, a fastening prominence is formed on a distal end of a finally folded auxiliary frame, and the main frames and the auxiliary frame are locked to each other in the folded status due to engagement between the engaging prominences and the fastening prominence.

Brief Description of the Drawings

The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which:

FIGs . 1 through 10 are views of a first embodiment of the present invention, wherein FIG. 1 is a partially enlarged perspective view illustrating an entire construction of a portable keyboard according to the first embodiment of the present invention;

FIG. 2 is an exploded perspective view of FIG. 1;

FIG. 3 is an exploded perspective view illustrating a structure of a key section of the portable keyboard according to the present invention;

FIG. 4 is a cross-sectional view illustrating an assembled status of FIG. 3 ; FIG. 5 is an exploded perspective view illustrating another structure of a key section of the portable keyboard according to the present invention;

FIG. 6 is an exploded perspective view of an auxiliary frame, illustrating support means and infrared beam communication means according to the present invention;

FIG. 7 is a partially enlarged perspective view illustrating an assembled status of the support means and infrared beam communication means of FIG. 6;

FIG. 8 is a perspective view illustrating an in-use status of the portable keyboard according to the present invention;

FIGs . 9a through 9f are perspective views sequentially illustrating a folding procedure of the portable keyboard according to the present invention; and FIG. 10 is a side cross-sectional view illustrating a folded status of the portable keyboard according to the present invention; and

FIGs. 11 through 18 are views of a second embodiment of the present invention, wherein FIG. 11 is a perspective view schematically illustrating an entire construction of a portable keyboard according to the second embodiment of the present invention;

FIG. 12 is a perspective view illustrating an unfolded status of the portable keyboard; FIG. 13 is an exploded perspective view illustrating support means according to the present invention;

FIG. 14 is a perspective view illustrating a state wherein a connector is accommodated in the portable keyboard according to the present invention; FIG. 15 is a partially enlarged perspective view illustrating a folded status of the portable keyboard according to the present invention;

FIG. 16a is a perspective view illustrating a coupled status of a variation of the support means according to the present invention;

FIG. 16b is a perspective view illustrating an uncoupled status of FIG. 16a;

FIG. 17 is a perspective view illustrating a folded status of the portable keyboard including the variation of the support means according to the present invention; and

FIG. 18 is a perspective view illustrating an in-use status of the portable keyboard including the variation of the support means according to the present invention.

Best Mode for Carrying Out the Invention Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts .

FIG. 1 is a partially enlarged perspective view illustrating an entire construction of a portable keyboard according to a first embodiment of the present invention. As shown in FIG. 1, in the portable keyboard according to this first embodiment of the present invention, first through fifth main frames 1, 1A, IB, IC and ID are arranged along a transverse direction, and one auxiliary frame 2 is arranged along a longitudinal direction with respect to the second main frame 1A. As can be readily seen from FIG. 2, the first through fifth main frames 1, 1A, IB, IC and ID and the auxiliary frame 2 are connected one with another by pairs of hinge shafts 3, 3A, 3B, 3C and 3D in manner such that they can be folded and unfolded about the pairs of hinge shafts 3 , 3A, 3B, 3C and 3D. At this time, the pairs of hinge shafts 3, 3A, 3B and 3C for connecting the first through fifth main frames 1, 1A, IB, IC and ID are parallelly arranged one to another, and the pair of hinge shafts 3D for connecting the auxiliary frame 2 to the second main frame 1A are perpendicularly arranged with respect to the pairs of hinge shafts 3, 3A, 3B and 3C. Each of the first through fifth main frames 1, 1A, IB, IC and ID has a key section 4 or 4A which includes one or more keys .

FIG. 3 is an exploded perspective view illustrating a structure of the key section 4 of the portable keyboard according to the present invention; and FIG. 4 is a cross- sectional view illustrating an assembled status of FIG. 3. As shown in FIGs. 3 and 4, the key section 4 comprises a contact connection circuit board 41 which is positioned on a bottom surface of the second main frame 1A, a rubber keypad 42 which is positioned on the contact connection circuit board 41 and has a bottom plate 42A and a plurality of rubber keys 42B, an attachment plate 43 which is positioned above the rubber keypad 42 and is defined with a plurality of rubber key insertion holes 43A corresponding to the rubber keys 42B so that the rubber keys 42B of the rubber keypad 42 can project upward through the rubber key insertion holes 43A, and a hard cap 44 which is bonded to upper ends of the rubber keys 42B projecting upward through the rubber key insertion holes 43A of the attachment plate 43.

A connector seating portion 10 is extendedly formed at one end of the second main frame 1A so that a connector 5 can be seated on the connector seating portion 10. The connector 5 is assembled to the connector seating portion 10 in a manner such that bolts are threaded through locking holes defined at both sides of the connector 5 and fastening holes defined at both sides of the connector seating portion 10. Also, as best shown in FIG. 1, a key, which is positioned on the pair of hinge shafts 3C, is divided into two key portions 44A and 44B so that the two key portions 44A and 44B can be folded along the hinge shafts 3C and operated as one key upon being unfolded. Of course, a person skilled in the art will readily appreciate that the key may be divided into three or more key portions . FIG. 5 is an exploded perspective view illustrating another structure of the key section 4A of the portable keyboard according to the present invention. As shown in FIG. 5, a key which is located on the third main frame IB to constitute the key section 4A, is distinguished from the keys located on the first, second, fourth and fifth main frames 1, 1A, IC and ID, due to a peculiarity of a shape of the third main frame IB which is formed to have a narrow width.

The key section 4A comprises a contact connection circuit board 41 which is positioned on a bottom surface of the third main frame IB and is formed to have a narrow width in correspondence to the shape of the third main frame IB, and a hard cap 40 which is positioned on the contact connection circuit board 41. The hard cap 40 is made of a thin resilient material and formed to have a length which corresponds to an entire length of the third main frame IB. Both ends of the hard cap 40 are supported by a pair of support ends 40A and 4OB which are formed to have contours respectively corresponding to those of both ends of the third main frame IB and are securely fixed to both ends of the third main frame IB. Between the support ends 40A and 4OB, the hard cap 40 is formed with a press part 40C. The press part 40C projects upward from a plane of the hard cap 40 by being bent and is formed on a lower surface thereof with a contact projection 40D. FIG. 6 is an exploded perspective view of the auxiliary frame, illustrating support means and infrared beam communication means according to the present invention.

As shown in FIG. 6, the auxiliary frame 2 is defined, on both sides and at one end thereof, a pair of shaft holes 21, in a manner such that the hinge shafts 3D arranged at the one end of the second main frame 1A are respectively fitted into the shaft holes 21. A pair of folded status maintaining protrusions 22 are projectedly formed on upper ends of both side walls of the auxiliary frame 2. Thus, as shown in FIG. 10, when the first through fifth main frames 1, 1A, IB, IC and ID are accommodated in the auxiliary frame 2 in a folded status, as two edges of a combination of the first through fifth main frames 1, 1A, IB, IC and ID are respectively grasped by the pair of folded status maintaining protrusions 22, the folded status of the combination is maintained as it IS .

Support means for supporting a portable information terminal 300 as shown in FIG. 8 is installed on the auxiliary frame 2. The support means includes a support plate 23 which is pivotably connected at one end thereof to the other end of the auxiliary frame 2 by a pivot shaft 23B. An infrared beam maintaining arch 24, which has at an upper part thereof an infrared optical element 24A, is positioned outward of the support plate 23. The infrared beam maintaining arch 24 is also pivotably connected at one end thereof to the other end of the auxiliary frame 2 by a pair of pivot shafts 24B. The infrared beam maintaining arch 24 is located so that it can be pivoted in an interlocked manner with the support plate 23.

The infrared beam maintaining arch 24 is formed by cutting out a bottom wall of the auxiliary frame 2, and the support plate 23 is formed by cutting out a portion of the infrared beam maintaining arch 24. In order to ensure that the support plate 23 is captured by the infrared beam maintaining arch 24 when the infrared beam maintaining arch 24 is pivoted, to be integrally pivoted with the infrared beam maintaining arch 24, as shown in FIG. 7, the support plate 23 is defined at lower ends of both sides thereof with a pair of engaging grooves 23A. A pair of resilient bars 24C are formed on inner edges of the infrared beam maintaining arch 24, and a pair of engaging projections 24D are formed on the pair of resilient bars 24C to be capable of being engaged into the pair of engaging grooves 23A, respectively.

An arch spring 24E is placed around the pivot shaft 24B of the infrared beam maintaining arch 24, in a manner such that one end of the arch spring 24E is fastened to the pivot shaft 24B and the other end of the arch spring 24E is fastened to the auxiliary frame 2. By biasing force of the arch spring 24E, when external force applied to the infrared beam maintaining arch 24 is removed, the infrared beam maintaining arch 24 is returned to its original position.

FIGs. 9a through 9f are perspective views sequentially illustrating a folding procedure of the portable keyboard according to the present invention.

As shown in FIG. 9, in this preferred embodiment of the present invention, as shown in FIG. 9a, the first main frame 1 and the fifth main frame ID are folded inward about the hinge shafts 3 and 3C so that they are overlapped onto the second main frame 1A and the fourth main frame IC, respectively, as shown in FIG. 9b. Then, after folding about the hinge shafts 3A the third main frame IB, as shown in FIG. 9c, which is formed to have a narrow width, the fourth main frame IC onto which the fifth main frame ID is overlapped is folded about the hinge shafts 3B as shown in FIG. 9d in such a way as to be overlapped onto the second main frame 1A onto which the first main frame 1 is overlapped.

Thereupon, in a state shown in FIG. 9e, by folding the auxiliary frame 2 about the hinge shafts 3D as shown in FIG. 9f, the folding procedure of the portable keyboard is completed. At this time, the first through fifth main frames 1, 1A, IB, IC and ID, which are accommodated in the auxiliary frame 2 , are maintained in the folded status because the two edges of the combination of the first through fifth main frames 1, 1A, IB, IC and ID are respectively grasped by the pair of folded status maintaining protrusions 22 as shown in FIG. 10.

FIG. 11 is a perspective view schematically illustrating an entire construction of a portable keyboard according to the second embodiment of the present invention. As shown in FIG. 11, in the portable keyboard according to this second embodiment of the present invention, first through fourth main frames 110, 110A, HOB and HOC are arranged along a transverse direction, and first and second auxiliary frames 120 and 130 are arranged along a longitudinal direction with respect to the first main frame 110. The first through fourth main frames 110, 110A, HOB and HOC are connected one with another by pairs of hinge shafts 140, 140A and 140B in manner such that they can be folded and unfolded about the pairs of hinge shafts 140, 140A and 140B, and the first and second auxiliary frames 120 and 130 are connected by pairs of hinge shafts 14OC and 14OD in a manner such that they can be folded and unfolded about the pairs of hinge shafts 14OC and 14OD. At this time, the pairs of hinge shafts 140, 140A and 14OB for connecting the first through fourth main frames 110, HOA, HOB and HOC are parallelly arranged one to another, and the pairs of hinge shaft 14OC and 14OD for connecting the first and second auxiliary frames 120 and 130 are perpendicularly arranged with respect to the pairs of hinge shafts 140, 140A and 140B. FIG. 12 is a perspective view illustrating an unfolded status of the portable keyboard.

As shown in FIG. 12, in the present embodiment of the present invention, as described above, the first through fourth main frames 110, HOA, HOB and HOC which are arranged in the transverse direction are foldably connected one with another by the pairs of hinge shafts 140, 140A and 140B, and the first and second auxiliary frames 120 and 130 which are arranged in the longitudinal direction are foldably connected to the first main frame 110 and the first auxiliary frame 120, respectively, by the pairs of hinge shafts 140C and 140D. Each of the first through fourth main frames 110, HOA, HOB and HOC has a plurality of keys which are made of soft material .

Marginal portions 160A and 160 are respectively formed at one ends of the first and fourth main frames 110 and HOC. A side wall portion 170 of a predetermined height is formed around a perimeter of each of the first and fourth main frames 110 and HOC having the marginal portions 160A and 160, to integrally extend upward, whereby lower and upper cases 190 and 180 are formed so that the second and third main frames HOA and HOB can be accommodated in the lower and upper cases 190 and 180 in a folded status.

A connector 121 for connecting a portable terminal 300 is integrally mounted to a lower part on an inner surface of the first auxiliary frame 120. Referring to FIG. 18, support means for supporting the portable terminal 300 connected to the connector 121 is composed of the first auxiliary frame 120 and the second auxiliary frame 130 which is foldably connected to the first auxiliary frame 120 by the pair of hinges shafts 140D. The portable terminal 300 is supported by the first auxiliary frame 120, and the second auxiliary frame 130 functions to hold the first auxiliary frame 120 at a desired angle .

In order not to interfere with the connector 121 integrally mounted to the first auxiliary frame 120 when the portable keyboard according to the present invention is folded, the second and third main frames HOA and HOB are not formed with any marginal portions at one ends thereof, and the marginal portion 160 of the fourth main frame HOC is defined at a middle portion thereof with an accommodating groove 180A in which the connector 121 of the first auxiliary frame 120 can be accommodated.

As locking means for locking the first through fourth main frames 110, HOA, HOB and HOC and the first and second auxiliary frames 120 and 130 to each other in a folded status, a pair of engaging prominences 190A are formed at the other end of the lower case 190 including the first main frame 110, and a fastening prominence 131 which can be engaged with the engaging prominences 190A is formed on a distal end of the second auxiliary frame 130.

FIG. 13 is an exploded perspective view illustrating the support means according to the present invention. As shown in FIG. 13, in this second embodiment of the present invention, the support means is composed of the first auxiliary frame 120 which is connected at one end thereof and in the longitudinal direction to one end of the lower case 190 including the first main frame 110, and the second auxiliary frame 130. The connector 121 is integrally mounted to the lower part on the inner surface of the first auxiliary frame 120. The second auxiliary frame 130 is foldably connected to the first auxiliary frame 120 by the pair of hinge shafts 140D formed at one end thereof. The other end of the first auxiliary frame 120 is formed with a pair of shaft holes (not shown) through which the pair of hinge shafts 140D of the second auxiliary frame 130 are inserted. FIG. 14 is a perspective view illustrating a state wherein the connector is accommodated in the portable keyboard according to the present invention; and FIG. 15 is a partially enlarged perspective view illustrating a folded status of the portable keyboard according to the present invention. As can be readily seen from FIG. 14, the second and third main frames HOA and HOB are folded to be accommodated in the lower and upper cases 190 and 180 including the first and fourth main frames 110 and HOC, respectively. When the first auxiliary frame 120 is folded onto the upper case 180, the connector 121 of the first auxiliary frame 120 is accommodated in the accommodating groove 180A of the upper case 180 without undergoing any interference. As the fastening prominence 131 which is formed at the distal end of the second auxiliary frame 130 connected to the first auxiliary frame 120 is engaged with the pair of engaging prominences 190A formed at the other end of the lower case 190, the folded status is effected as shown in FIG. 15.

FIG. 16a is a perspective view illustrating a coupled status of a variation of the support means according to the present invention; and FIG. 16b is a perspective view illustrating an uncoupled status of FIG. 16a. As shown in FIGs. 16a and 16b, as in the second embodiment of the present invention, the support means according to this variation is composed of the first auxiliary frame 120 which is foldably connected to the lower case 190 including the first main frame 110 and the second auxiliary frame 130 which is foldably connected to the fist auxiliary frame 120. At this time, the second auxiliary frame 130 comprises a rod member 132 of which both ends are bent parallel to each other. As shown in FIG. 16b, both ends of the rod member 132 are respectively inserted into a pair of shaft holes 122 which are defined at both sides of the other end of the first auxiliary frame 120, so as to serve as the pair of hinge shafts 140D connecting the first and second auxiliary frames 120 and 130 with each other. Adjacent to each shaft hole 122 defined in the first auxiliary frame 120, a support shoulder 123 is formed in such a way as to extend in the longitudinal direction. Here, the reference numeral 131A represents a fastening rod portion. FIG. 17 is a perspective view illustrating a folded status of the portable keyboard including the variation of the support means according to the present invention. As the fastening rod portion 131A of the second auxiliary frame 130 which comprises the rod member 132 is engaged with the pair of engaging prominences 190A formed at the other end of the lower case 190, the folded status is effected.

Industrial Applicability

As apparent from the above descriptions, the portable keyboard according to the present invention provides advantages in that, since the portable keyboard can be folded and unfolded as an input device for a portable information terminal or a desktop computer, occupies a reduced volume and has a small thickness in a folded status so as to decrease an entire weight thereof, and can serve in an unfolded status as a normally sized conventional keyboard which can be manipulated using both hands, the portable keyboard can be easily carried along with a portable information terminal, thereby securing portability. Also, because the portable keyboard has a simple construction and realizes operational accuracy, a manufacturing cost is reduced and operational reliability is ensured.

Further, according to the present invention, by the communication using an infrared optical element, the portable keyboard according to the present invention accomplishes compatibility of a connector with respect to various portable information terminals having connectors which are differently shaped depending upon a manufacturer or a model . Moreover, due to the fact that the portable keyboard according to the present invention uses a rubber keypad and a hard cap is attached to upper surfaces of rubber keys of the rubber keypad, soft touch of the rubber keypad can be maintained as it is. Furthermore, since a height of each key is decreased, the wrist can feel comfortable upon using the keyboard .

Claims

1. A portable keyboard characterized in that at least four main frames, which are arranged along a transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in a longitudinal direction; at least one auxiliary frame is foldably connected with one of the four main frames by a pair of hinge shafts which extend in the transverse direction; each of the four main frames includes a key section having one or more keys; a connector is mounted to one of the four main frames or the auxiliary frame; support means for supporting a portable information terminal is installed on the auxiliary frame; and the auxiliary frame includes locking means for locking the main frames and the auxiliary frame to each other in a folded status.

2. The portable keyboard as claimed in claim 1 , wherein five main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction.

3. The portable keyboard as claimed in claim 1, wherein four main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction.

4. The portable keyboard as claimed in claim 1, wherein five main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction; and one auxiliary frame is foldably connected with a second main frame by the pair of hinge shafts which extend in the transverse direction.

5. The portable keyboard as claimed in claim 4 , wherein the five main frames and one auxiliary frame are connected one with another by the respective pairs of hinge shafts which extend in the longitudinal and transverse directions, in a manner such that they can be folded inward onto another frame.

6. The portable keyboard as claimed in claim 1, wherein four main frames, which are arranged along the transverse direction, are foldably connected one with another by respective pairs of hinge shafts which pairs are parallel one to another, with each hinge shaft extending in the longitudinal direction; and two auxiliary frames are foldably connected with a first main frame by two pairs of hinge shafts which extend in the transverse direction.

7. The portable keyboard as claimed in claim 6 , wherein the support means is composed of first and second auxiliary frames, the connector is integrally mounted to a lower part on an inner surface of the first auxiliary frame, marginal portions are respectively formed at one ends of first and fourth main frames of which side walls respectively delimit lower and upper cases, and the marginal portion of the fourth main frame is defined with an accommodating groove in which the connector of the first auxiliary frame can be accommodated.

8. The portable keyboard as claimed in claim 1 , wherein a key, which is positioned on at least one folding line between two adjoining main frames, is divided into at least two key portions so that the two key portions can be folded along the folding line and operated as one key upon being unfolded.

9. The portable keyboard as claimed in claim 4 , wherein the auxiliary frame includes an infrared beam maintaining arch which has at an upper part thereof an infrared optical element and which possesses a support plate capable of being moved in an interlocked manner therewith, and the infrared optical element is arranged in a manner such that it can be maintained at a predetermined angle by the infrared beam maintaining arch.

10. The portable keyboard as claimed in claim 9, wherein the support plate is defined at both sides thereof with a pair of engaging grooves in a manner such that movement of the holder pate can be limited by a pair of resilient bars formed on inner edges of the infrared beam maintaining arch and a pair of engaging projections formed on the pair of resilient bars to be engaged into the pair of engaging grooves, and the infrared beam maintaining arch is elastically biased by an arch spring toward its original position.

11. The portable keyboard as claimed in claim 1, wherein the key section of the main frame comprises a contact connection circuit board which is positioned on a bottom surface of the main frame and has a plurality of contacts; a rubber keypad which is positioned on the contact connection circuit board and has a plurality of rubber keys corresponding to the contacts; an attachment plate which is defined with a plurality of rubber key insertion holes corresponding to the rubber keys so that the rubber keys of the rubber keypad can project upward through the rubber key insertion holes; and a hard cap which is bonded to upper ends of the rubber keys projecting upward through the rubber key insertion holes of the attachment plate.

12. The portable keyboard as claimed in claim 1 , wherein the locking means is configured in a manner such that a pair of folded status maintaining protrusions are formed on upper ends of both side walls of the auxiliary frame, and the main frames and the auxiliary frame are locked to each other in the folded status .

13. The portable keyboard as claimed in claim 1, wherein the locking means is configured in a manner such that a pair of engaging prominences are formed on an outer surface of a finally folded main frame, a fastening prominence is formed on a distal end of a finally folded auxiliary frame, and the main frames and the auxiliary frame are locked to each other in the folded status due to engagement between the engaging prominences and the fastening prominence.