GB1591865A - Circuit element mounting assemblies - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO CIRCUIT ELEMENT MOUNTING ASSEMBLIES (71) We, A.R.D. TECHNICAL ASSISTANCE & ENGINEERING SER VICES INTERNATIONAL ANSTALT, of P.O. Box 34613, 9490 Vaduz, Liechtenstein, a body corporate organised and existing under the laws of Liechtenstein, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- In Patent 1 483 577 there is disclosed and claimed a heat sink assembly for mounting an electric circuit element and an electric circuit board, the assembly comprising a first pair of substantially parallel spaced metal plates, a second pair of substantially parallel spaced metal plates which extend substantially at right angles to the first pair of plates, each of the first pair of plates being in good thermal contact with at least one of second pair of plates, the electric circuit board being spacedly supported between and substantially parallel to the first pair of plates, and means on one of the first pair of plates and the circuit board for mounting a circuit element within the volume bounded by the second pair of plates, the circuit board and the said one plate of the first pair of plates.

In accordance with the present invention there is provided a modified form of this assembly for electrostatic shielding of electric circuit elements mounted therewithin.

The invention accordingly provides an electrostatic shielding assembly for mounting electric circuit boards, the assembly comprising a pair of spaced substantially parallel elongate metal plates having one side closed by a third elongate metal plate extending substantially at right angles to the pair of plates and in good electrical contact with at least one thereof, the side opposite said one side being without an electrically conductive closure, an electric circuit board supported within the assembly so as to be substantially parallel to and spaced from the third metal plate, and a circuit element mounted within the assembly on the side of the circuit board remote from the third plate.

The circuit element can comprise a second circuit board extending substantially parallel to the pair of plates towards the said one side of the assembly.

The opposite side can be at least partially closed by means extending across between the free ends of the pair of plates but making no contribution to the electrostatic shielding function of the assembly. Such a means can provide support for the second circuit board.

Conveniently, a plate of plastics or other electrically non-conductive material, having the general form of the top plate 90 shown in figure 4 of Specification 1 483 577 can be carried by the pair of plates.

The present invention will be more readily understood from the following illustrative description and accompanying drawing, in which the single figure is an end view of an electrostatic shielding assembly in which the invention is embodied.

The assembly illustrated comprises a pair of parallel like extruded plates 2, one turned relative to the other so that upper flanges 4 and lower flanges 6 of each plate extend inwardly.

A channel shaped extruded base plate 5 has a base wall 8 provided with external ridges 10 and side walls 12 formed with inwardly facing steps on which rest the lower ends of the side walls 2. The plates 2 and 6 are secured together by any suitable fastening means so as to be in good electrical contact; they thus together form a channel providing electrostatic shielding for any electric circuit elements received therein.

A first circuit board 15 extends across between the side plates 2 and is secured beneath the lower flanges 6. The board 15 is also secured to the underside of a base flange 16 of a generally I-section extruded plate 17 which extends upwardly to divide the space between the plates 2. The plate 17 thus shields electric circuit elements between it and either plate 2 from such elements between it and the other plate 2.

As shown in the right hand side of the figure, the board 15 mounts to the right of the plate 17 a circuit element in the form of a resistor 20; in practice a plurality of different circuit components will be so mounted. As shown on the left hand side of the figure, the board mounts to the left of the plate 17 a circuit element in the form of a second circuit board 22, by means of a connection block 24; the board will itself mount circuit components in use, although such components are not shown.

The illustrated assembly as so far described will function satisfactorily to support and electrostatically shield the electric circuit components it contains. In some applications, it may be desired to close or partially close the open top of the assembly and this can be done by means for example of a strip 25 of plastics material which as shown on the right of the figure rests on the upper flange 4 of the plate 2 and the upper flange 26 of the plate 17. If the assembly contains a circuit board such as the board 22 and it is desired to support this board at its top, the plate 2 can be replaced by a generally T-shaped plastics member 28 as shown on the left of the figure; the downwardly extending wall of the member 28 has a step accommodating the upper edge of the board 22 and the portion extending below this edge overlaps the board to permit supporting connection to be made thereto.

The assembly of the present invention is not intended for dissipation of a great amount of heat from the circuit elements it contains, but the ridges 10 provide for air flow beneath the base plate 5 and the plates can be rigid, for example, to increase their surface area and thus assist heat dissipation. In other respects the assembly resembles that of Specification 1 483 577 to which reference may be made for further particulars regarding construction, constructional variations, intended uses, and the like.

WHAT WE CLAIM IS: 1. An electrostatic shielding assembly for mounting electric circuit boards, the assembly comprising a pair of spaced substantially parallel elongate metal plates having one side closed by a third elongate metal plate extending substantially at right angles to the pair of plates and in good electrical contact with at least one thereof, the side opposite said one side being without an electrically conductive closure, an electric circuit board supported within the assembly so as to be substantially parallel to and spaced from the third metal plate, and a circuit element mounted within the assembly on the side of the circuit board remote from the third plate.

2. An assembly as claimed in claim 1 wherein the circuit element comprises a second circuit board.

3. An assembly as claimed in claim 1 or 2 wherein said opposite side is at least partially closed by a member which does not contribute to the electrostatic shielding function of the assembly.

4. An assembly as claimed in claim 3 wherein the member is connected to the circuit element.

5. An assembly as daimed in claim 3 or 4 wherein the member is of plastics material.

6. An assembly as claimed in claims 3, 4 or 5 wherein the pair of plates have internally extending flanges at or adjacent the open side, and the member engages the flanges.

7. An assembly substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. a resistor 20; in practice a plurality of different circuit components will be so mounted. As shown on the left hand side of the figure, the board mounts to the left of the plate 17 a circuit element in the form of a second circuit board 22, by means of a connection block 24; the board will itself mount circuit components in use, although such components are not shown. The illustrated assembly as so far described will function satisfactorily to support and electrostatically shield the electric circuit components it contains. In some applications, it may be desired to close or partially close the open top of the assembly and this can be done by means for example of a strip 25 of plastics material which as shown on the right of the figure rests on the upper flange 4 of the plate 2 and the upper flange 26 of the plate 17. If the assembly contains a circuit board such as the board 22 and it is desired to support this board at its top, the plate 2 can be replaced by a generally T-shaped plastics member 28 as shown on the left of the figure; the downwardly extending wall of the member 28 has a step accommodating the upper edge of the board 22 and the portion extending below this edge overlaps the board to permit supporting connection to be made thereto. The assembly of the present invention is not intended for dissipation of a great amount of heat from the circuit elements it contains, but the ridges 10 provide for air flow beneath the base plate 5 and the plates can be rigid, for example, to increase their surface area and thus assist heat dissipation. In other respects the assembly resembles that of Specification 1 483 577 to which reference may be made for further particulars regarding construction, constructional variations, intended uses, and the like. WHAT WE CLAIM IS:

1. An electrostatic shielding assembly for mounting electric circuit boards, the assembly comprising a pair of spaced substantially parallel elongate metal plates having one side closed by a third elongate metal plate extending substantially at right angles to the pair of plates and in good electrical contact with at least one thereof, the side opposite said one side being without an electrically conductive closure, an electric circuit board supported within the assembly so as to be substantially parallel to and spaced from the third metal plate, and a circuit element mounted within the assembly on the side of the circuit board remote from the third plate.

2. An assembly as claimed in claim 1 wherein the circuit element comprises a second circuit board.

3. An assembly as claimed in claim 1 or 2 wherein said opposite side is at least partially closed by a member which does not contribute to the electrostatic shielding function of the assembly.

4. An assembly as claimed in claim 3 wherein the member is connected to the circuit element.

5. An assembly as daimed in claim 3 or 4 wherein the member is of plastics material.

6. An assembly as claimed in claims 3, 4 or 5 wherein the pair of plates have internally extending flanges at or adjacent the open side, and the member engages the flanges.

7. An assembly substantially as herein described with reference to the accompanying drawing.