BACKGROUND OF THE INVENTION &null;0001&null; 1. Field of the Invention &null;0002&null; The present invention relates to power key assemblies usable in electronic devices, such as mobile phones. &null;0003&null; 2. Related art &null;0004&null; Electronic devices need a source of power during operation. Some of them contain batteries which provide power. Most electronic devices need a power switch to switch power on or off as needed. One solution is to combine the function of a power key with another key. For instance, in some mobile phones, the power switch is actuated by pressing the &null;no&null; key for a relatively long time. However, this solution has several problems. Such multi-function keys require a more complicated link pattern between the key and the printed circuit board (PCB) in the device. Additionally, keys combining more than one function are used more often than if the same keys are provided separately, which can shorten the life of the key. Moreover, if the key is shielded by a flip cover or similar device, the user must open the cover to actuate the key, which makes operation more inconvenient. SUMMARY OF THE INVENTION &null;0005&null; An object of the present invention is to provide a power key assembly which has relatively high reliability and which can be operated more conveniently. &null;0006&null; To accomplish the above-mentioned objects, the present invention provides a power key assembly for a mobile phone. The power key assembly comprises a front shell, a power key and a switch element. The front shell includes a face plate and two opposite side walls, a top wall and a bottom wall projecting perpendicularly from edges of the face plate. A collar-like receiving portion is integrally molded in the top wall. The power key is received in the receiving portion. The switch element is arranged on a printed circuit board (PCB) and engages with the power key. A keypad includes a plurality of keys and the keys are received in corresponding openings defined through the face plate. The PCB mechanically engages with said front shell and mechanically and electrically engages with said keypad. &null;0007&null; Further objects and advantages of the present invention will become more apparent from a consideration of the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS &null;0008&null; FIG. 1 is an exploded, perspective view of a lower element of a mobile phone having a power key assembly of the present invention; &null;0009&null; FIG. 2 is an exploded, perspective view of a power key assembly of the present invention; &null;0010&null; FIG. 3 is a perspective view of a power key assembly of the present invention assembled with a keypad and a printed circuit board; and &null;0011&null; FIG. 4 is similar to FIG. 3, but viewed from another aspect.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT &null;0012&null; A power key assembly in accordance with the present invention is installed in an electronic device. In the embodiment shown in FIG. 1, the electronic device is a lower element 1 of a foldable mobile phone. The lower element 1 includes a front shell 10, a keypad 20, a printed circuit board (PCB) 30, and a back shell 40, which includes a back cover 41 and a battery cover 42. The power key assembly comprises a power key 51, a switch element 52, and the front shell 10 of the mobile phone. &null;0013&null; Referring to FIG. 2, the front shell 10 includes a substantially rectangular face plate 100 defining a plurality of openings 102 therethrough and forming two opposite side walls 103, a top wall 104 and a bottom wall 105 perpendicularly projecting from the face plate 100. The face plate 100 and the walls 103, 104, 105 cooperatively define a space wherein the keypad 20 can be mounted. The openings 102 are a little larger than corresponding keys (not shown) located on the keypad 20, for receiving the keys therein. A plurality of clasps 106 are formed on walls 103, 104, 105 for engaging with the PCB 30 and the back cover 41. In particular, a pair of clasps 106 are disposed on the top wall 104 and a receiving portion 107 is formed between the pair of clasps 106, integrally molded in the top wall 104. The receiving portion 107 defines a through hole 108 therein. &null;0014&null; The power key 51 has a base portion 512, a press portion 510 extending from the base portion 512, and a resisting portion 514 (see FIG. 4) extending through the base portion 512 from the press portion 510. The base portion 512 is hollow in structure. An exterior diameter of the base portion 512 is larger than a diameter of the through hole 108. The press portion 510 is correspondingly smaller than that of the through hole 108 of the receiving portion 107, whereby the press portion 510 can be received in the through hole 108. The switch element 52 is attachable to the PCB 30 such that, in assembly it is adjacent to the top wall 104 of the front shell 10. The switch element 52 includes a main portion 522, an elastic portion 520 movably engaged in the main portion 522, and a solder portion 524 for soldering the switch element 52 onto the PCB 30. The main portion 522 encloses certain circuits communicating with power switch circuits (not shown) on the PCB 30, which can switch a power connection on or off. Note that most of the functional components are omitted on the PCB 30 for simplicity. &null;0015&null; Referring to FIGS. 3 and 4, in assembly, the keypad 20 is mounted to the front shell 10. Keys on the keypad 20 are received in corresponding openings 102 defined in the front shell 10. The power key 51 is movably engaged with the front shell 10, with the press portion 510 being received in the through hole 108 and the base portion 512 firmly abutting against the receiving portion 107. In a non-depressed state, the press portion 510 protrudes out of the through hole 108 for users to press. The PCB 30 with the switch element 52 soldered thereon mechanically engages with the front shell 10 and mechanically and electrically engages with the keypad 20. The elastic portion 520 of the switch element 52 engages with the resisting portion 514 of the power key 51. The back cover 41 snappingly engages with the front shell 10, and the battery cover 42 is received in the back cover 41. &null;0016&null; In operation, to connect power to the lower element 1, a user presses the press portion 510 of the power key 51. The press portion 510 moves inwardly, pushing the resisting portion 514 against the elastic portion 520 of the switch element 52. The elastic portion 520 thus moves inwardly to make connections between certain circuits (not shown) arranged in the main portion 522. Since such circuits electrically connect with power switch circuits (not shown) arranged on the PCB 30, a power connection is created. A battery inside the battery cover 42 is thereby connected to provide power to the lower element 1. To disconnect the power connection, the user presses the press portion 510 of the power key 51 again. The elastic portion 520 of the switch element 52 is forced to return its original position, thereby switching off the power connection. The battery then stops providing power to the lower element 1. &null;0017&null; The power key assembly in accordance with the present invention has better reliability since the receiving portion 107 is integrally molded in the top wall 104 of the front shell 10 rather than being separately assembled with the top wall 104. This integration ensures that the receiving portion 107 is not prone to be deformed during assembly. In addition, when this power key assembly is used in an electronic device, such as a foldable mobile phone, the user can turn the phone on or off without opening the cover thereof, thereby increasing the convenience of use. Furthermore, the power key 51 and the switch element 52 can be firmly assembled with the front shell 10, the keypad 20 and the PCB 30, providing a firmly integrated subassembly which facilitates production assembly. &null;0018&null; It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. |