Extendable antenna device

Abstract: An extendable antenna device which is reducible in length when accommodated and ensures enough elasticity at an area of junction to a housing of a radio device. A first elongated flexible antenna section (24) is connected slidably with a second antenna section (25). A hold mechanism is provided which holds the first antenna section against the housing of the radio device, and which accommodates and holds the first and second antenna sections in the housing of the radio device.

Description: This invention relates to an extendable antenna device suitable for small-sized radio devices such as a portable radio telephone set, which is made elastic at a portion mechanically connected to the radio device so as to prevent breakage of the antenna device, as well as to ensure the safety and the convenience of the users. A variety of studies in miniaturization of radio devices have been made together with the spread of portable telephone sets. In order to achieve such miniaturization, the antenna must be accommodated in the radio device at least when the device is not used. The structure of the antenna today is basically of a 5/8λ- whip type, and has an impedance matching unit built in the device, and antenna elements extended from the transmitter or receiver in use. FIGs. 8 and 9 show a conventional antenna device which extends its antenna element in use and accommodates it within the device. In FIGs. 8 and 9, reference numeral 1 denotes a housing of a radio device; 2, a whip antenna; and 3, a printed board. As shown in FIG. 10, whip antenna 2 includes a body 5. a knob 6 attached to a tip of the antenna body, a stop 7 provided at the base of the antenna body, and a housing junction 8 which attaches antenna 2 to housing 1. Antenna body 5 is made of a flexible material such as piano wire or wire cable so as to absorb external force applied to the antenna body by bending itself elastically. Antenna body 5 extends through a hole 10 in junction 8. Antenna body 5. base 11 and tip 12 are sized so as to fit into hole 10. Provided on junction 8 is a hollow cylindrical support composed of suspended flexible rectangular tongues 13 which hold base 11 and ensure electrical connection between antenna body 5 and junction 8. In antenna 2. junction 8 is fixedly screwed into housing 1. Antenna 2 and printed board 3 are electrically connected via a high-frequency connector lead 15. Since whip antenna 2 is attached to housing 1 in the above arrangement. it is accommodatable into housing I when it is not used to thereby facilitate its conveYance. Telephone communication is easily achieved when antenna 2 is extended by pulling the knob 6. In order to completely accommodate antenna 2 into housing I in this radio device, it is necessary to reduce the length of antenna 2 compared with the length of housing 1. If the length of antenna 2 is adjusted to the length of the housing 1 of such a radio device which will be miniaturized every year, antenna 2 would become too short, so that the directionality and gain of the antenna are insufficient and hence the radio performance is deteriorated. It would be conceivable to use a rod antenna which includes a plurality of extendable cylindrical antenna elements instead of a whip antenna. However, since a rod antenna of this type has insufficient flexibility, a load is likely to be applied to the base of the antenna due to vibrations generated during conveyance or installation of a portable radio device which uses the antenna to thereby cause breakage. One example is that of US-A-2735932. In order to eliminate this drawback, it is known to provide a coil spring at the base of a rod antenna. However, according to this method, the structure itself is complicated, so that manufacture is difficult, and the device is expensive and likely to be broken. Furthermore, even if the antenna is accommodated, part of the coil spring extends out of the housing to thereby render it inconvenient to carry the device. As described above, when the conventional whip antenna device is of the type which is accommodated in the housing of the radio device, it cannot be longer than the length of the housing, and hence it cannot obtain a length satisfying an appropriate wavelength for the device. If the rod antenna is used instead of the whip antenna, it has inconveniences in that it cannot sufficiently withstand vibration and shock. US-A-2932367 discloses a vehicle-mounted rod antenna which can be bent relative to its mounting and which can be extended telescopically, but this cannot be retracted within the vehicle. By way of background, also, US-A-3435456 discloses a whip antenna mounted rotatably outside a radio device. US-A-2 735 932 discloses a rod antenna for a compact radio equipment which can be telescopically extended and retracted within the casing of the compact radio equipment. Accordingly, the invention provides an extendable antenna device as defined in Claim 1, and a radio device including such an antenna. The length of the antenna is sufficiently extendable compared with the housing when it is used. When extended, stresses are likely to be greatest over that part of the first antenna section which is connected to the housing, and this part of the first antenna section is made flexible, so that it can sufficiently withstand vibration and shock. No alleviating spring coils are needed, so that manufacture of the extendable antenna device is easy. FIG. 1 is a cross section view of the essential portion of one embodiment of an extendable antenna device according to the present invention; FIG. 2 is a perspective view of a portable radio device having the extendable antenna device of the embodiment; FIG. 3 is a perspective view of the extendable antenna device of the embodiment; FIGS. 4(a) and (b) are a cross section view of the extendable antenna device shown in FIG. 3 and illustrating an extension and retraction of the antenna; FIGS. 5(a), (b) and (c) are a cross section view of the antenna device and illustrating an extension and retraction of the antenna relative to the radio device; FIG. 6 is a perspective view of another embodiment of the extendable antenna device according to the present invention; FIGs. 7(a) and (b) are a cross section view of the antenna device of FIG. 6 and illustrating its extension and retraction; FIG. 8 is a perspective view of a conventional portable radio device; and FIG. 9 is a cross section view of the essential portion of the conventional antenna device. One embodiment of the present invention will now be described in detail with reference to FIGs. I and 5. FIG. 2 is a perspective view of a portable radio device with an extendable antenna device according to the present invention. FIG. 1 is a cross section view of the essential portion of FIG. 2. Reference numeral 20 denotes the housing of a radio device; 21, an extendable antenna which is either hollow or solid; and 22, a printed board. As shown in FIG. 3, antenna 21 includes an antenna body 26 which includes a whip antenna section 24 and a hollow cylindrical antenna section 25, a knob 27 attached to an end of cylindrical antenna section 25, a stop 28 provided at the base of the whip antenna section 24 and a housing junction 29 to attach antenna 21 to housing 20. Whip antenna section 24 is made of a flexible core material such as piano wire or wire cable coated with a resin such as polyacetal. As shown in FIG. 4, one end of whip antenna section 24 is inserted in hollow cylindrical antenna section 25 which is held slidable along whip antenna section 24. In that case, as shown in FIG. 1, an elastic engagement portion 31 provided at an end of whip antenna 24 surface contacts the inner wall of cylindrical antenna 25, which is slidable along whip antenna section 24 while keeping electrical connection with whip antenna section 24. FIG. 4(a) shows extendable antenna 21 which is extended to its maximum length in which case cylindrical antenna section 25 is prevented from slipping off from whip antenna section 24 by a reduced end 25a of antenna section 25 engaged with the engagement portion 31. FIG. 4(b) shows antenna 21 retracted to its shortest length where whip antenna section 24 is accommodated in cylindrical antenna section 25. Cylindrical antenna section 25 and the base 33 of whip antenna section 24 are the same size in outer diameter. As shown in FIG. 1, housing junction 29 has a hole 34 through which whip antenna section 24 extends. Hole 34 is sized so as to fittingly receive the base 33 of whip antenna 24 and hollow cylindrical antenna 25. Housing junction 29 has a hollow cylindrical support composed of suspended flexible tongues 36. The outer diameter of antenna section 24 is small compared with the inner diameter of the cylindrical support, the outer diameters of base 33 and cylindrical antenna section 25 are slightly large compared with the cylindrical support. The tongues 36 cooperate to hold the base 33 of whip antenna section 24 at the position of FIG. 1 to ensure electrical connection with housing junction 29. The holding force between whip antenna section 24 and cylindrical antenna section 25 through engagement portion 31 is set so as to be smaller than that between the base 33 of whip antenna section 24 and tongues 36 through the tongues. As shown in FIG. 1, antenna 21 is attached to housing 20 by screwing housing junction 29 into a female threaded hole 38 provided in housing 20. Antenna 21 is electrically connected via a high-frequency connector lead 39 to printed board 22. The extension and retraction of the extendable antenna device of this embodiment will now be described with reference to FIGs. 5 (a), (b) and (c). FIG. 5(a) shows an extended antenna of the antenna device. In this state, the reduced end 25a of hollow cylindrical antenna section 25 is engaged with engagement portion 31, the base 33 of whip antenna section 24 is held in flexible contact with hold tongues 36 of housing junction 29, and stop 28 abuts on the end of tongues 36. Under such condition, if knob 27 of cylindrical antenna section 25 is pressed toward the housing for retraction, whip antenna section 24 is slidably accommodated within cylindrical antenna section 25, the engagement portion 31 of whip antenna section 24 abuts on knob 27 of cylindrical antenna section 25 due to the difference between the holding force between whip and cylindrical antenna sections 24 and 25 via engagement portion 31, and the holding force between base 33 of whip antenna section 24 and tongues 36 via the tongues. This causes the flexible hold between base 33 and tongues 36 to be released, and the antenna section is accommodated within the radio device 20, as shown in FIG. 5(b). When hollow cylindrical antenna section 25 arrives at the position of support tongues 36 of housing junction 29, the outer surface of cylindrical antenna section 25 is flexibly held by tongues 36 and knob 27 of antenna section 25 abuts on housing junction 29, whereby the accommodation of the antenna into the housing is completed (FIG. 5(c)). When the antenna is extended, cylindrical antenna section 25 is pulled out, and then the base 33 of whip antenna section 24 is put into contact with and held by tongues 36. Even when the antenna is accommodated in the radio device 20, cylindrical antenna section 25 is still electrically connected via tongue 36 of housing junction 29 with printed board 22. Therefore. antenna 21 performs its antenna function even when accommodated in the radio device. Thus. an additional built-in antenna and change-over means for switching between the built-in antenna and antenna 21 is unnecessary. According to the present invention, the radio device functions even when antenna 21 is accommodated into the housing. Extendable antenna 21 is mounted to housing 20 of the radio device in the above arrangement, so that when antenna 21 need not be used. it is retracted in the direction of arrow b so as to be accommodated in housing I as shown in FIG. 2. When accommodated in housing I, antenna 21 does not stick out from housing 20. Therefore, the radio device radio device is easy to carry, and also easy to place in a limited space. Since cylindrical antenna section 25 fits in hole 34 in housing junction 29, antenna 21 will not come out from housing 20 and stick out by vibrations which may occur when it is being carried. By pulling knob 25 in the direction of arrow a (FIG. 1), antenna 21 can be extended to the extent of the sum of the lengths of whip and cylindrical antenna sections 24 and 25, so that the length of antenna 21 can be sufficiently longer than the length of housing 20. Large stresses are likely to apply particularly to the part of whip antenna section 24 connected to housing 20. According to the present invention, this part is made of highly flexible whip antenna section 24. Therefore, even if an external force is applied to antenna 21 when the radio device is being carried or when it is installed, antenna 21 is sufficiently flexible enough to absorb the external force. FIG. 6 illustrates another embodiment of the extendable antenna device according to the present invention. In the particular embodiment, a two-stage antenna including hollow cylindrical antenna sections 250 and 251 is connected to whip antenna section 240. Antenna body 260 includes whip antenna section 240 and cylindrical antenna sections 250 and 251. Knob 270 is provided at an end of cylindrical antenna section 251, a stop 280 is provided at the base of whip antenna section 240, and housing junction 290 and tongue 360 are provided. An engagement portion 310 which flexibly contacts the inner surface of hollow cylindrical antenna 250 is provided at an end of whip antenna section 240, as shown in FIG. 7(a). A second engagement portion 311 which flexibly contacts the inner surface of hollow cylindrical antenna section 251 is provided at an end of cylindrical antenna section 250. FIG. 7(a) illustrates the antenna which is extended to its maximum length. FIG. 7(b) illustrates the antenna which is retracted to its minimum length. In that case, the engagement portion 311 of cylindrical antenna section 250 abuts on knob 270 of hollow cylindrical antenna section 251, and engagement portion 310 of whip antenna section 240 abuts on engagement portion 311 of cylindrical antenna 250. The holding force between the cylindrical antenna sections 250 and 251 through engagement portion 311 is set so as to be smaller than that between whip antenna section 240 and cylindrical antenna section 250 through engagement portion 310 while the holding force between whip antenna section 240 and cylindrical antenna section 250 through engagement portion 310 is set so as to be smaller than that between whip antenna section 240 and tongues 360 through the tongues. Although the hollow cylindrical antenna section connected to the whip antenna section has been illustrated as having a two-stage structure in the particular embodiment, it may have a three-stage or higher multi-stage strucure. The extendable antenna device according to the present invention may be not only used in a portable radio device, but also may be used in a wide variety of radio devices including television sets and radio sets.

Claims: An extendable antenna device for use in a radio device, comprising: a first, flexible, elongate antenna section (24); a second elongate, hollow antenna section (25) broader than the first antenna section (24) and connected telescopically with and over one end of the first antenna section: and a junction (29) for holding said first antenna section relative to a housing (20) of said radio device; characterised in that the end of the first, flexible elongate antenna section (24) lying outside the second elongate antenna section (25) is connected to a base (33) which is held in the junction (29) when the antenna is extended in use, and in that the second elongate antenna section (25) is slidable within the junction (29) to allow its retraction through the junction (29) into the housing once the first section (24) has retracted telescopically into the second section (25). An extendable antenna device according to claim 1, wherein said second antenna section (25) is shorter than the first antenna section (24). An extendable antenna device according to claim 1 or 2, wherein said second antenna section (25) has a cylindrical body. An extendable antenna device according to any preceding claim, wherein the end of said first antenna section (24) lying within the second antenna section (25) includes an engagement portion (31) for flexibly contacting the internal surface of the second antenna section (25). An extendable antenna device according to any preceding claim, wherein said base (33) is substantially equal in outer diameter to said second antenna section (25). An extendable antenna device according to any preceding claim, wherein said junction (29) has a hole through which said second antenna section (25) is slidable and a flexible contact portion (36) for supporting either said base (33) of said first antenna section (24) or said second antenna section (25), depending on the degree of extension of the antenna, by flexibly contacting said base or said second antenna section. An extendable antenna device according to claim 6 as appendant to claim 4, wherein the holding force between said engagement portion (31) of said first antenna section (24) and said second antenna section (25) is smaller than the holding force between the base (33) of said first antenna section (24) and said flexible contact portion (36) of said junction (24). An extendable antenna according to any preceding claim, wherein said second antenna section (25) includes an at least two-stage antenna (250,251, Figs. 6 and 7). An extendable antenna device according to any preceding claim, wherein said first flexible elongated antenna section (24) and said second antenna section (25) include preventing means (25a,31, Fig. 4(a)) for preventing said second antenna section from slipping off said first antenna section. An extendable antenna device according to claim 9, wherein said preventing means comprises: an engagement portion (31) on said first antenna section, and a reduced end (25a) of said second antenna section for engaging with said engaging portion. An extendable antenna device according to claim 8, wherein said second antenna section (25) is shorter than the length of said first antenna section (240), and wherein the at least two-stage antenna (250,251, Fig. 6) comprises an inner section (250) received telescopically in an outer section (251) which is shorter than, or equal to, the length of said inner section (250). An extendable antenna device according to claim 8 or 11, wherein said inner section (250) and said outer section (251) each include a hollow cylindrical body, wherein said inner section slidably receives the first antenna section (240) therein, and wherein said outer section (251) slidably receives said inner antenna section (250). An extendable antenna device according to claim 12, wherein said first antenna section (240) includes at one end a first engagement portion (310) which flexibly contacts the inner surface of said inner section (250), and wherein said inner section (250) includes at one end a second engagement portion (311) which flexibly contacts the inner surface of said outer antenna section (251). An extendable antenna device according to claim 13, wherein said base (33) of said first antenna section (240) is substantially equal in outer diameter to said outer section (251). An extendable antenna device according to claim 14 when appendant to claim 6, wherein the holding force between said inner section (250) and said outer section (251) through the second engagement portion (311) is set so as to be smaller than that between said first antenna section (240) and said inner section (250) through said first engagement portion (310), and wherein the holding force between said first antenna section (240) and said inner antenna section (250) through said first engagement portion (310) is set so as to be smaller than that between said first antenna section (240) and said flexible contact portion (360). A radio device having a housing (20) and an extendable antenna device according to any preceding claim, the junction (29) being held by the housing, wherein said first antenna section (24) is shorter than the length of said housing (24). A radio device according to claim 16, wherein said first antenna section (24) electrically contacts at its base (33) said junction (29) so that it is electrically connected with an electric circuit in the device when said antenna device is extended, and wherein said second antenna section (25) electrically contacts said junction (29) so that it is electrically connected with said electric circuit when said antenna device is retracted and accommodated in the housing. A radio device according to claim 16 or 17, wherein said second antenna section (25) is capable of being accommodated in said housing such that said second antenna section (25) covers the first antenna section (24). A radio device according to claim 16, 17 or 18, wherein said first antenna section (24) capable of being drawn out of the housing such that its engagement portion (31) is engaged with an end (25a) of said second antenna section (25).

Inventors: KOIKE NOBORU, KOIKE, NOBORU, KOIKE, NOBORU C/O INTELLECTUAL PROPERTY DIVISION
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1989
Main classification: H01Q1
IPC codes: H01Q1