GB2170658A

GB2170658A - A casing for an electrical appliance

Info

Publication number: GB2170658A
Application number: GB08531458A
Authority: GB
Inventors: Hideo Kitamura
Original assignee: Omron Tateisi Electronics Co
Current assignee: Omron Corp
Priority date: 1984-12-27
Filing date: 1985-12-20
Publication date: 1986-08-06
Also published as: GB8531458D0; JPH0739262Y2; JPS61114638U; GB2170658B

Abstract

A casing for an electrical appliance which includes a main case (1), a base plate (5) fitted into an open bottom portion (2) of the main case (1), first stand-off projections (3) having a large amount of protrusion (X) and provided to project from the lower edge (1a) of the main case (1), and second stand- off projections (6) having a small amount of protrusion (Y) and provided to project from the undersurface of the base plate (5) for providing two kinds of clearance between the undersurface of the base plate (5) and the surface of a printed circuit board. <IMAGE>

Description

SPECIFICATION A casing for an electrical appliance The present invention generally relates to a casing for an electrical appliance such as an electromagnetic relay, transformer or the like inductive circuit, which is to be mounted on a printed circuit board.

In a known form of a casing for an electrical appliance which is to be mounted on a printed circuit board, it has been so arranged that, in order to prevent flux from entering the interior of the appliance during soldering, and also, owing to necessity for removing or washing flux adhering to the undersurface of the casing and the corresponding surface of the printed circuit board for cleaning, stand-off projections or small projections (hereinafter referred to as stand-off projections) are formed on the reverse face of the undersurface of the casing so as to space said undersurface of the casing from the surface of the printed circuit board by the amount of protrusion of said stand-off projections, in order to thereby provide a predetermined clearance therebetween.

Meanwhile, there are cases where cleaning or washing of flux is effected by "FREON' (Registered Trade Mark) or by soap solution.

In the case of cleaning by the soap solution, the clearance as referred to above may be smaller than that in the cleaning by ''FREON'', thus resulting in reduction of height of the electrical appliance when the casing is actually mounted on the printed circuit board.

Accordingly, in the electrical appliance of the above described type which is to be mounted on a printed circuit board, it is of considerable inconvenience, even in products for the same kind of model, that two types of casings must be prepared, i.e., one type having large stand-off projections for the cleaning by "FREON" and the other type having small stand-off projections for the cleaning by soap solution. Furthermore, since the difference in the degrees or amounts of protrusion between the large stand-off projection and the small stand-off projection referred to above is only approximately 0.3 mm, it is extremely difficult to differentiate one from the other through visual inspection.

It is an object of the present invention, to provide an improved casing for an electrical appliance, which is capable of selecting two kinds of clearances between the undersurface of the casing and the corresponding surface of a printed circuit board for efficient cleaning.

Another object of the present invention is to provide a casing for an electrical appliance of the above described type, which has a simple structure and can be readily manufactured at low cost for use with various kinds of electrical appliances.

In accomplishing these and other objects, according to one preferred embodiment of the present invention, in a casing for an electrical appliance such as an electromagnetic relay, transformer or the like, there are provided on the undersurface of the casing, two kinds of stand-off projections different in the degrees of protrusion from said undersurface, thus making it possible to provide two kinds of clearances between the undersurface of the casing and the corresponding surface of the printed circuit board.

More specifically, in the case where the large clearance is required, the casing is mounted on the printed circuit board as it is.

On the other hand, when the small clearance is sufficient for the purpose, the casing is mounted on the printed circuit board by cutting the stand-off projections having the large amount of protrusion, or by forming holes at portions of the circuit board corresponding in positions thereto.

By the arrangement of the present invention as described above, an improved casing for an electrical appliance has been advantageously provided through simple construction.

The present invention will now be described in greater detail by way of example, with reference to the accompanying drawings, in which like parts are identified by like reference numerals, wherein: Figure 1 is a perspective view of a casing for an electrical appliance according to one preferred embodiment of the present invention; Figure 2 is an exploded perspective view of the casing of Figure 1; and Figure 3 is a side elevational view of the casing of Figure 1, which has been mounted on a printed circuit board.

Referring now to the drawings, there is shown in Figures 1 and 2, a casing for an electrical appliance according to one preferred embodiment of the present invention, which includes a main case 1 of a rectangular cubic box-like configuration open at its bottom portion 2, and a base plate 5 mounted thereon with an electrical or electronic part or component (now shown) having its terminals 10 extending downwardly from the base plate 5, with said base plate 5 being fitted into the open bottom portion 2 of the main case 1 so that its undersurface 5a is flush with the lower edge la of said main case 1.

A plurality of stand-off projections 3 (for example, four stand-off projections 3 in this embodiment) each having the amount of protrusion X are provided on the lower edge la of the main case 1 so as to extend downwardly therefrom, while another set of standoff projections 6 (for example, four stand-off projections 6 in this embodiment) each having the amount of protrusion Y are provided to extend downwardly from the undersurface 5a of the base plate 5. The amount of protrusion X of the stand-off projection 3 is equivalent to a clearance required between the surface of a printed circuit board 20 (Figure 3) and the undersurface 5a of the base plate 5 during cleaning by Freon, while the amount of protrusion Y of the other stand-off projection 6 is equivalent to a clearance required therebetween during cleaning by the soap solution.

As shown in the drawings, the stand-off projections 3 are in the form of a rectangular parallelepiped, and the stand-off projections 6 are cylindrical.

Accordingly, in the case where the large clearance is required for the cleaning by Freon, the casing is actually mounted on the printed circuit board 20 as it is as shown in Figure 3. In this case, the lower ends of the stand-off projections 3 are brought into contact with the surface of the printed circuit board 20 to provide the large clearance equivalent to the amount of protrusion X. Meanwhile, when the small clearance is sufficient for the purpose in the cleaning by the soap solution, either the stand-off projections 3 are cut off, or holes (not particularly shown) are preliminarily formed in the printed circuit board 20 in the positions corresponding to said stand-off projections 3.By the above arrangement, the lower ends of the stand-off projections 6 for the small clearance come into contact with the surface of the printed circuit board 20, whereby the casing can be mounted on the circuit board 20 through the small clearance equivalent to the amount of protrusion Y.

It should be noted here that in the foregoing embodiment, although the stand-off projections 3 are provided on the lower edge 1a of the case 1, with the stand-off projections 6 being provided on the undersurface 5a of the base plate 5, the positions for providing the stand-off projections are not limited to the above, but it may be so modified, for example, that both of the stand-off projections 3 and 6 are provided on the base plate 5. In this case, however, the stand-off projections 3 should preferably be provided at the peripheral portion for facilitation of cutting and prevention of faulty cutting, when it is taken into account that there are cases where such stand-off projections 3 are to be cut off as described above.

As is clear from the foregoing description, according to the present invention, owing to the provision of the two kinds of stand-off projections having different amounts of protrusion from the undersurface of the casing, it has become possible to provide the large and small clearances through selections of the stand-off projections for constact with the surface of the printed circuit board, with only one kind of casing being required for the manufacture. Although the difference between the amounts of protrusion of the two kinds of stand-off projections is rather small, it is not so difficult to distinguish the difference since these projections are to be provided side by side on the same surface, preferably in different shapes.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it will be appreciated that various changes and modifications will be apparent to those skilled in the art.

Claims

1. A casing for an electrical appliance which comprises a main case, and first and second stand-off projections provided on the undersurface of said main case so as to project downwardly therefrom by different amounts of protrusion.

2. A casing for an electrical appliance according to claim 1, further including a base plate fitted into an open bottom portion of said main case, with the undersurface of said base plate being flush with a lower edge of said main case.

3. A casing for an electrical appliance according to claim 1, wherein said first stand-off projections with a large amount of protrusion are provided to project from the lower edge of said main case, and said second standoff projections with a small amount of protrusion are provided to project from the undersurface of said base plate.

4. A casing for an electrical appliance according to claim 2, wherein said first stand-off projections with a larger amount of protrusion and said second stand-off projections with a small amount of protrusion are both provided to project from the undersurface of said base plate.

5. A casing for an electrical appliance according to any one of the preceding claims, wherein said first stand-off projections are in the form of rectangular parallelpipeds.

6. A casing for an electrical appliance according to any one of the preceding claims, wherein said second stand-off projections are cylindrical.

7. A casing for an electrical appliance according to any one of the preceding claims, wherein there are four first stand-off projections and four second stand-off projections.

8. An electrical appliance which includes a main case, a base plate on which an electrical component is mounted, with its terminals extending downwardly from said base plate and which is fitted into an open bottom portion of said main case, with the undersurface of said base plate being adapted to be flush with the lower edge of said main case, first stand-off projections having a large amount of protrusion and provided to project from the lower edge of said main case, and second stand-off projections having a small amount of projection and provided to project from the undersurface of said base plate.

9. A casing for an electrical appliance constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.