Unit with shield

A unit with shield includes a sub-circuit board (20). This sub-circuit board (20) is covered by a first shield plate (12) and second shield plate (14) engaged with each other through the sub-circuit board (20), and inserted in a hole (24) formed in a main circuit board (22). At this time, a first spring (36a) and second spring (36b), formed in an insertion (34) of the first shield plate (12), urges the sub-circuit board 20 against one surface of the hole (24), thereby fixing the sub-circuit board 20 in the hole (24). Also, the main circuit board (22) is clamped by an abutment portion (20a) formed in the sub-circuit board 20 and a removal preventing portion (38) formed in the first shield plate (12).

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a unit with shield, and more particularly to a
 unit with shield having a shield plate covering a sub-circuit board to be
 inserted and mounted in a hole formed in a main circuit board.
 2. Description of the Prior Art
 Prior art of this kind is disclosed in a publication of Japanese Utility
 Model Laying-open No. 77400/1988 laid open to the public on May 23, 1988.
 This prior art is provided with terminals as mounting legs on a
 sub-circuit board covered by a shield plate in order to enable the
 sub-circuit board to be mounted onto a main circuit board.
 In the prior art, however, there has been a problem of process complication
 in providing terminals on a sub-circuit board, resulting in an increase in
 manufacturing costs.
 SUMMARY OF THE INVENTION
 Therefore, it is a primary object of the present invention to provide a
 unit with a shield which is simple in structure but capable of inserting
 and fixing a sub-circuit board in a hole formed in a main circuit board.
 A unit with shield according to the present invention has: a shield plate
 covering over a sub-circuit board to be inserted into a hole formed in a
 main circuit board; a first shield plate and a second shield plate which
 are engaged through the sub-circuit board to cover over respective main
 surfaces of the sub-circuit board; and a spring portion provided in a
 lower portion of the first shied plate and inserted into the hole.
 As for main and back surface sides of the sub-circuit board, the first
 shield plate and the second shield plate are inserted in a hole formed in
 the lower portion of the main circuit board. Accordingly, the sub-circuit
 board is covered over and hence shielded by the first shield plate and
 second shield plate which are engaged with each other through the
 sub-circuit board.
 According to the present invention, the sub-circuit board and the first and
 second shield plates (unit with shield) can be positively fixed on the
 main circuit board by merely inserting the spring portion in the hole
 formed in the main circuit board. Consequently, structure is simplified
 and cost is reduced as compared to the conventional.
 The above spring portion includes a first spring and a second spring
 provided on respective surfaces of the lower portion of the first shield
 plate. Due to this, the spring portion provided in the lower portion of
 the first shield plate is inserted in the hole of the main circuit board,
 whereby the unit with shield, i.e. the sub-substrate and the first and
 second shield plates, is fixed on the main circuit board.
 In one aspect of the present invention, the spring portion urges the
 sub-circuit board against one surface of the hole whereby a pattern formed
 on the sub-circuit board and a pattern formed on a backside of the main
 circuit board are brought into close contact with each other. It is
 therefore possible to positively solder between the patterns by dipping.
 In another aspect of the present invention, because a removal preventing
 portion is provided in the lower portion of the first shield plate, the
 sub-circuit board, first shield plate and second shield plate are
 prevented from being removed from the main circuit

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A unit with shield 10 shown in FIG. 1 includes a first shield plate 12 and
 a second shield plate 14 that are formed of a conductive material, for
 example, a metal. The first shield plate 12 and the second shield plate 14
 are engaged with each other through a sub-circuit board 20, by engagements
 of engaging portions 16a and 16b of the first shield plate 12 with the
 engaging portions 18a and 18b of the second shield plate 14, thereby
 covering the sub-circuit board 20.
 That is, the first shield plate 12 and the second shield plate 14 are each
 made as a metal case having a bottom and an opposing opening. The opening
 of the second shield plate 14 is closed by the first shield plate 12
 whereby two main surfaces of the sub-circuit board 20 are provided with
 shields. The sub-circuit board 20 covered with the first shield plate 12
 and second shield plate 14 (FIG. 1) is inserted in a hole 24 formed in a
 main circuit board 22, as shown in FIG. 2.
 Referring further to FIG. 1, the sub-circuit board 20 has one main surface
 (parts side) 26 mounted with appropriate parts 28. The parts side 26 is
 covered over by the first shield plate 12. Also, the other main surface
 (pattern side) 30 is formed with a pattern 32 in an appropriate form. The
 pattern side 30 is covered by the second shield plate 14 in areas except
 for a lower portion thereof. That is, the lower portion of the pattern
 side 30 is not shielded but exposed outside.
 The first shield plate 12 has an insertion portion 34 extending down from
 the engaging portion 16b. The insertion portion 34 has a first spring 36a
 and a second spring 36b formed by metal coining to form ribs that project
 on opposite sides from the insertion portion 34. A removal preventing
 portion 38 is further formed underneath the first and second springs 36 by
 coining. The removal preventing portion 38 projects toward the front of
 the insertion portion 34, that is, in the same direction of the first
 spring 36a.
 The first spring 36a is bent in a bow form in a direction toward an inner
 periphery of the hole 24, as will be well understood from FIG. 2. When the
 unit with shield 10 is inserted into the hole 24, the first spring 36a
 comes into abutment against the inner periphery of the hole 24. Meanwhile,
 the second spring 36b is bent in a direction toward the parts side 26, and
 abuts against the parts side 26 at its lower portion.
 The removal preventing portion 38 projects toward a front of one main
 surface of the insertion portion 34, i.e. toward inner periphery of the
 hole 24. The removal preventing portion 38 at its top end abuts against a
 backside of the main circuit board 22 whereby the unit with shield 10 is
 prevented from being removed out of the hole 24.
 As will be well understood from FIG. 3, the insertion portion 34 is
 provided lower left and right in the first plate 12. Each of the insertion
 portions 34 has a first spring 36a and second spring 36b arranged
 horizontally parallel with each other while a removal preventing portion
 38 is formed intermediate between the first spring 36a and the second
 spring 36b. Furthermore, steps are formed in the lower portion of the
 sub-circuit board 20. These steps respectively provides abutment portions
 20a. These abutment portions 20a are to be abutted against a top surface
 of the main circuit board 22.
 If the unit with shield is inserted into the hole 24 formed in the main
 circuit board 22, the first spring 36a of the insertion portion 34 comes
 into contact with one inner periphery of the hole 24 to have a force. This
 force is to be applied to the pattern side 30 of the sub-circuit board 20
 through the second spring 36b. That is, the unit with shield 10 is fixed
 in the hole 24 due to a force of the first spring 36a that urges the
 pattern side 30 against the other inner periphery of the hole 24.
 By urging pattern side 30 against the inner periphery of the hole 24, the
 first pattern 32 formed on the pattern side 30 and the second pattern 40
 formed on the backside of the main circuit board 20 are brought into close
 contact with each other. Accordingly, the first pattern 32 and the second
 pattern 40 are positively soldered during dipping without causing
 deviation in their positions.
 Furthermore, the sub-circuit board is vertically positioned in position by
 abutting the abutting portion 20a of the sub-circuit board 20 against the
 top surface of the main circuit board 22 as well as abutting the removal
 preventing portion 38 against the underside of the main circuit board 22.
 Incidentally, the first spring 36a and the second spring 36b can be
 modified into various forms, such as a trapezoidal form and a clip form,
 besides the triangular form shown. These springs, if formed in a
 trapezoidal form, will increase an abutment area against the inner surface
 of the hole 24, providing closer contact of the sub-circuit board 20 with
 the main circuit board 22.
 Although the present invention has been described and illustrated in
 detail, it is clearly understood that the same is by way of illustration
 and example only and is not to be taken by way of limitation, the spirit
 and scope of the present invention being limited only by the terms of the
 appended claims.