Tuner that prevents cover detachment from frame

The tuner has a frame with a mounting leg attached to a motherboard. Thus, when fitting a nut, the frame is not rotated, so that the detachment of the cover is prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENT The configuration of a tuner according to the present invention will be described below with reference to FIGS. 1 to 4 . Referring now to FIGS. 1 to 4 , a square frame 1 , formed of metal plates, has first and second rectangular sidewalls 1 a and 1 b provided so as to oppose each other, third and fourth sidewalls 1 c and 1 d provided between edges of the first and second sidewalls 1 a and 1 b so as to oppose each other, opening portions 1 e and 1 f that are open in the upper and lower directions, respectively, and mounting legs 1 g and 1 h that project downward from the first and second sidewalls 1 a and 1 b. Partitioning walls 2 , formed of metal plates, are installed in the frame 1 such that the inside of the frame 1 is divided into a plurality of regions to provide compartments 3 a , 3 b , and 3 c. A circuit board 4 (schematically shown in FIGS. 2 and 3 ) has a wiring pattern, and an OSC (oscillator) circuit, IF circuit, RF circuit, and the like, all of which are not shown herein, are formed on the circuit board 4 . The circuit board 4 is arranged and supported in the frame 1 by appropriate means. In this case, the OSC circuit is located in the compartment 3 a , the IF circuit is in the compartment 3 b , and the RF circuit is in the compartment 3 c , which are electrically shielded from one another by the partitioning walls 2 . Each of the circuits has a grounding pattern (not shown), which is part of the wiring pattern, connected to the frame 1 by soldering. An upper cover 5 , formed of a thin metal plate, has a rectangular flat-plate portion 5 a and elastic lips 5 b that have been bent downward from the four edges of the flat-plate portion 5 a . The cover 5 is attached to the frame 1 with the elastic lips 5 b holding the frame 1 such that the flat-plate portion 5 a covers the upper opening 1 e of the frame 1 . A lower cover 6 , formed of a thin metal plate, has a rectangular flat-plate portion 6 a , elastic lips 6 b that have been bent upward from the four edges of the flat-plate portion 6 a , and a pair of mounting lips 6 c and 6 d which oppose each other and which project downward. The cover 6 is attached to the frame 1 with the elastic lips 6 b holding the frame 1 such that the flat-plate portion 6 a covers the lower opening 1 f of the frame 1 . When the cover 6 is attached to the frame 1 , as shown in FIG. 4 , the mounting lip 6 c is located at the side of the first sidewall 1 a adjacent to the RF circuit, while the mounting lip 6 d is located at the side of the second sidewall 1 b adjacent to the OSC circuit. The cover 6 is attached to the frame 1 with the elastic lips 6 b elastically holding the frame 1 . In addition, the mounting legs 1 g and 1 h , provided at the frame 1 , extend beyond the plate portion 6 a of the cover and project downward therefrom. A threaded coaxial connector 7 includes a threaded portion 8 a made of metal, a flanged portion 8 b connected to the threaded portion 8 a , a sleeve portion 8 c connected to the flanged portion 8 b , an insulator 9 provided in a hole 8 d in the center of the threaded portion 8 a , and a center conductor 10 attached to the insulator 9 of the hole 8 d. The threaded coaxial connector 7 is attached in such a manner that the sleeve portion 8 c is installed in the first side wall 1 a of the frame 1 by swaging and the center conductor 10 , which is for input, is connected to the RF circuit. The mounting lip 6 c of the cover 6 is located adjacent to the threaded coaxial connector 7 . The tuner of the present invention configured in this manner is accommodated in electronic equipment (not shown), and the mounting lips 6 c and 6 d of the lower cover 6 and the mounting legs 1 g and 1 h are soldered to the grounding pattern (not shown) of a motherboard 11 . Further, the threaded portion 8 a of the threaded coaxial connector 7 is inserted into a hole 12 a of a chassis 12 and a nut 13 is fitted through the threaded portion 8 a , thereby allowing the tuner to be installed. When the nut 13 is fitted through the threaded coaxial connector 7 , the frame 1 is apt to rotate; however, the mounting legs 1 g and 1 h of the frame 1 are fixed to the motherboard 11 , so that the frame 1 is not rotated. This prevents the cover 6 detaching from the frame 1 . In addition, the cover 6 is formed of a thin metal plate and the elastic-lips 6 b elastically hold the frame 1 . Thus, in general, the flat-plate portion 6 a between the first sidewall 1 a , at the side of which the RF circuit is located and to which the threaded coaxial connector 7 is installed, and the second sidewall 1 b , at the side of which the OSC circuit is located, tends to have resistance and to be in an unstable condition due to insufficient grounding. This may cause an oscillation signal from the OSC circuit to Jump into the center conductor 10 , giving rise to interference leading to noise. However, according to the tuner of the present invention, the cover 6 is directly connected to the grounding pattern of the motherboard 11 by the mounting lips 6 c and 6 d , adjacent to the OSC circuit and the threaded coaxial connector 7 of the RF circuit. This secures the grounding of the cover 6 and eliminates the jumping of the oscillation signal into the threaded coaxial connector 7 , thereby reducing the noise. In the above embodiment, while the description has been given for, the case in which the mounting lips 6 c and 6 d of the cover 6 are respectively,provided at the sides of first and second sidewalls 1 a and 1 b , at least one the mounting lips may be provided at one side of the first sidewall 1 a and second sidewall 1 b . Additionally, the mounting lips may be provided adjacent to the threaded coaxial connector 7 and the OSC circuit, that is, not only at the sides of the first and second sidewalls 1 a and 1 b but also at the sides of the third and fourth sidewalls 1 c and 1 d. In addition, with reference to the mounting legs that have been provided at the frame 1 , the mounting leg or legs may be provided at either one of the first to fourth sidewalls or at two or more of the first to fourth sidewalls. In the tuner of the present invention, since the mounting legs 1 g of the frame 1 is fixed to the motherboard 11 , the frame 1 is not rotated when the nut 13 is fitted through the threaded coaxial connector 7 . This prevents the detachment of the cover 6 . The cover 6 has mounting lips, which are provided adjacent to the threaded coaxial connector 7 or the OSC circuit and which protrude downward, for mounting the tuner on the motherboard 11 . This secures the grounding of the cover 6 and eliminates the jumping of the oscillation signal into the threaded coaxial connector 7 , thereby reducing the noise. Furthermore, since the mounting lips 6 c and 6 d that are provided at the cover 6 are respectively arranged adjacent to the threaded coaxial connector 7 and the OSC circuit, the arrangement according to the present invention can further secure the grounding of the cover 6 and eliminate the jumping of the oscillation signal into the threaded coaxial connector 7 , thereby further reducing the noise. Additionally, since the plurality of mounting legs 1 g and 1 h are provided at the sidewalls, the arrangement according to the present invention can enhance the mounting strength of the frame 1 to the motherboard 11 . That is, when fitting the nut 13 , the frame is not rotated, which prevents detachment of the cover 6 . In addition, the mounting lips 6 c and 6 d are provided at the side of the first sidewall 1 a and at the side of the second sidewall 1 b opposing the first sidewall 1 a , respectively, and the first sidewall 1 a and the second sidewall 1 b have mounting legs 1 g and 1 h , respectively, the tuner according to the present invention can enhance the mounting strength of the frame 1 and secure the grounding of the cover 6 .