GB2291938A

GB2291938A - Gaskets for housings

Info

Publication number: GB2291938A
Application number: GB9415781A
Authority: GB
Inventors: Brian Andrew Croker
Original assignee: APW Electronics Ltd
Current assignee: APW Electronics Ltd
Priority date: 1994-08-04
Filing date: 1994-08-04
Publication date: 1996-02-07
Anticipated expiration: 2014-08-04
Also published as: GB9415781D0; GB2291938B

Abstract

A panel 10 or other component of a housing for electrical or electronic equipment is provided with a physical gasket 30 to limit ingress of dust, water and foreign bodies and an electro-magnetic gasket 24 to limit transmission of electro-magnetic radiation into and/or out of the housing. In order to secure the gaskets 30, 24 to the panel 10 and to provide good electrical contact between the electro-magnetic gasket 24 and the panel 10: the panel 10 is formed with a channel 16; the electro-magnetic gasket is placed in the channel 16 against an electrically conductive side wall 20 thereof; a trail of material is applied along the channel between the electro-magnetic gasket 24 and the other side wall 18; and the material is expanded and cured so as to form the physical gasket 30 which is adhered to the other side wall 18 and the electro-magnetic gasket 24 and so as to apply compression to the electro-magnetic gasket 24 so that it is pressed against the electrically conductive side wall 20. <IMAGE>

Description

GASKETS FOR HOUSINGS This invention relates to gaskets for housings, such as gaskets between panels and/or doors and/or other housing components of housings for, for example, electrical or electronic equipment.

The invention is more particularly concerned with "physical" gaskets for limiting or preventing the ingress of dust, water and foreign bodies, and "electro-magnetic" gaskets for limiting or preventing the transmission of electro-magnetic radiation, for example radio frequency radiation, into and/or out of the housing. It will be appreciated that many electro-magnetic gaskets may also function to some extent as physical gaskets, but in the context of this specification the terms "physical" gaskets and "electro-magnetic" gaskets are used to mean gaskets whose primary purposes are as mentioned above.

It is known to provide electro-magnetic gaskets between separable components of a housing, and one known electro-magnetic gasket comprises a strip of soft but resilient plastics or rubbery material which is sheathed with meshed or braided electrically conductive material. Desirably, the gasket is fixed to one of the housing components in electrical contact therewith, and makes electrical contact with the other housing component, for example when the housing is assembled if one of the components is a removable panel, or when the door is closed if one of the components is a door. Difficulties have been encountered in the prior art in securing the electro-magnetic gasket to the housing component to provide a reliable mechanical and electrical connection in a simple manner.

It is also known to provide a physical gasket by laying a trail of a foamable, liquid or paste, polyurethane material on the housing component. The material cures to provide a rubbery gasket of an appropriate resilience which bonds strongly to the housing component.

In accordance with one aspect of the present invention, there is provided a method of applying a gasket to a housing component, comprising the steps of: providing a channel in the housing component, the channel having a pair of opposed side walls, at least one of the side walls having an electrically conductive surface; laying an elongate electro-magnetic gasket along the channel and applying an elongate trail of a material along the channel so that the electro-magnetic gasket is adjacent said one side wall and so that the trail is between the electro-magnetic gasket and the other side wall, the material being such that it can expand and adhere and cure to form a resilient material; and permitting or causing the material to expand and adhere and cure so as to form a physical gasket alongside the electro-magnetic gasket so that the electro-magnetic and physical gaskets are in compression between the side walls of the channel, and so that the physical gasket is adhered to the channel and to the electro-magnetic gasket.

Thus the invention provides not only a combination of a physical gasket and an electro-magnetic gasket, but also uses the physical gasket to adhere the electro-magnetic gasket to the housing component.

Furthermore, the invention uses the expansion of the material while curing to cause the electro-magnetic gasket to be pressed against the electrically conductive side wall of the channel to provide good electrical contact therebetween. Referring to the known physical gasket described above, it is known that the trail of material expands as it cures, and this is a disadvantage in that the size of the cured gasket differs from the size of the trail which is laid. The present invention turns this disadvantage into an advantage by using the expansion to improve the electrical contact of the electro-magnetic gasket.

The method preferably includes the step of at least temporarily holding the electro-magnetic gasket in position prior to applying the trail of material. In one example, this is done by applying adhesive tape to the electro-magnetic gasket and the housing component.

Alternatively, or additionally, the channel may be provided with a first deeper channel portion in which the electro-magnetic gasket is laid, and a second shallower channel portion in which the trail of material is applied.

Preferably, the rate of application of the material is controlled such that, after the material has expanded and cured, the electromagnetic gasket projects further from the channel than the physical gasket. Also, the electro-magnetic gasket and the material are preferably chosen such that, after the material has expanded and cured, the electro-magnetic gasket is softer than the physical gasket. Thus, in use when the gaskets abut another housing component, the electromagnetic gasket is squashed more than the physical gasket to provide good electrical contact between the electro-magnetic gasket and the other housing component.

In accordance with another aspect of the present invention, there is provided a gasketted housing component, wherein: the housing component has a channel formed therein, the channel having a pair of opposed side walls, at least one of the side walls having an electrically conductive surface; an elongate electro-magnetic gasket extends along the channel adjacent said one side wall; an elongate; resilient physical gasket extends along the channel adjacent the other side wall, the physical gasket being of an expanded and cured material; the physical gasket is adhered to the channel and the electromagnetic gasket; and the electro-magnetic and physical gaskets are in compression between the side walls of the channel.

In either aspect of the invention, said material is preferably a two-part mix of a first component having Polyol as a major component and a second component having Isocyanate as a major component.

In one embodiment, the side walls of the channel are substantially parallel for simplicity of formation of the channel.

Alternatively, in another embodiment, the side walls of the channel diverge in the direction into the channel, so that the physical and electro-magnetic gaskets are keyed into the channel.

The housing component may be, for example, a panel, door or pillar.

In accordance with a further embodiment of the present invention, there is provided a housing comprising having a gasket ted housing component defined above and a second housing component having a surface against which the electro-magnetic and physical gaskets abut.

There follows a description of an example of the method of the invention and embodiments of the apparatus of the invention, with reference to the accompanying drawings in which: Figures 1A to 1E are sectional views through an edge of a door panel illustrating an example of the method of the invention; and Figures 2 and 3 are cross-sectional views through the edge of the door panel showing alternative arrangements of a channel therein.

Referring to Figure 1A, a door panel 10 formed of sheet metal, such as steel, has its edge stiffened by folding of the metal to form a pair of parallel ribs 12, 14. A channel 16 is formed between the ribs 12, 14 and has left and right side walls 18, 20 and a bottom wall 22. At least the right side wall is plated so as to have a corrosionresistant, electrically conductive surface.

Referring to Figure 1B, an electro-magnetic gasket 24 of known construction is placed in the channel 16 so as to rest on the bottom wall 22 of the channel and to abut the right side wall 20 of the channel. The electro-magnetic gasket 24 may be in the form of a strip of soft material which is covered by a braided or meshed sheath of electrically conductive material, or it may be of a soft material which is electrically conductive throughout. The electro-magnetic gasket 24 is rectangular in cross-section and projects out of the channel 16. A gap 26 remains between the electro-magnetic gasket 24 and the left side wall 18 of the channel.

Referring to Figure 1C, a trail 28 of a material is applied along the channel 16 in the gap 26 between the electro-magnetic gasket 24 and the left side wall 18. The material is a two-part mix of mainly Polyol and mainly Isocyanate sold under the name Fermapor K31 by the company Sonderhoff of Germany. The material is supplied through a metering station to a mixing head which is mounted on a robot arm so that the rate and position of application of the trail 28 can be precisely controlled.

Referring to Figure 1D, shortly after the trail 28 of material is laid, it begins to foam and expand, and as it cures it hardens and adheres to the left side wall 18 and part of the bottom wall 22 of the channel 16, and to the left side of the electro-magnetic gasket 24.

Referring to Figure 1D, the amount of material which is applied is controlled so that, once it is cured, it forms a physical gasket 30 which projects out of the channel 16 by a lesser distance than the electro-magnetic gasket 24, and which, due to sideways expansion, causes the electro-magnetic gasket 24 also to be in compression in the left-right direction so that good electrical contact is ensured between the right side of the electro-magnetic gasket and the electrically conductive surface of the right side wall 20 of the channel 16. Once cured, the physical gasket 30 has a hardness of between 8 and 20 shore A, and the electro-magnetic gasket 24 has a substantially lower hardness.

Referring to Figure 1E, the door panel 10 is shown closed against a further panel or pillar 32 having an electrically conductive flat surface 34 against which both the electro-magnetic gasket 24 and the physical gasket 30 abut. In this state, the electro-magnetic gasket 24 is compressed in the up-down direction to ensure good electrical contact with the pillar 32, and the physical gasket 30 is also compressed. It is expected that the physical gasket 30 can provide an index of protection of IP66 according to DIN40050.

Figure 2 shows a modification to the arrangement described above.

In Figure 2, the left and right side walls 18, 20 of the channel 16 diverge in the direction into the channel to provide a keying effect to assist further in holding the physical and electro-magnetic gaskets in the channel 16.

In the modification shown in Figure 3, the bottom wall of the channel 16 is stepped to form a deeper channel portion 16a to receive the electro-magnetic gasket 24, and a shallower channel portion 16b to receive the physical gasket 30. The riser 18a of the step serves to assist in holding the electro-magnetic 24 in position prior to the expansion and curing of the physical gasket 30.

It will be appreciated that many other modifications and developments may be made to the invention. For example, there are numerous other materials which can expand and cure to form the physical gasket 30. Also, the electro-magnetic gasket need not be rectangular in cross-section.

Claims

1. A method of applying a gasket to a housing component, comprising the steps of: providing a channel in the housing component, the channel having a pair of opposed side walls, at least one of the side walls having an electrically conductive surface; laying an elongate electro-magnetic gasket along the channel and applying an elongate trail of a material along the channel so that the electro-magnetic gasket is adjacent said one side wall and so that the trail is between the electro-magnetic gasket and the other side wall, the material being such that it can expand and adhere and cure to form a resilient material; and permitting or causing the material to expand and adhere and cure so as to form a physical gasket alongside the electro-magnetic gasket, so that the electro-magnetic and physical gaskets are in compression between the side walls of the channel, and so that the physical gasket is adhered to the channel and to the electro-magnetic gasket.

2. A method as claimed in claim 1, further comprising the step of at least temporarily holding the electro-magnetic gasket in position prior to applying the trail of material.

3. A method as claimed in claim 2, wherein the electro-magnetic gasket is temporarily held in place by applying adhesive tape to the electro-magnetic gasket and the housing component.

4. A method as claimed in claim 2 or 3, wherein the electro-magnetic gasket is held in place by providing the channel with a first deeper channel portion in which the electro-magnetic gasket is laid, and a second shallower channel portion in which the trail of material is applied.

5. A method as claimed in any preceding claim, wherein the rate of application of the material is controlled such that, after the material has expanded and cured, the electro-magnetic gasket projects further from the channel than the physical gasket.

6. A method as claimed in any preceding claim, wherein the electromagnetic gasket and the material are chosen such that, after the material has expanded and cured, the electro-magnetic gasket is softer than the physical gasket.

7. A method of applying a gasket to a housing component, substantially as described with reference to the drawings.

8. A gasketted housing component, wherein: the housing component has a channel formed therein, the channel having a pair of opposed side walls, at least one of the side walls having an electrically conductive surface; an elongate electro-magnetic gasket extends along the channel adjacent said one side wall; an elongate, resilient physical gasket extends along the channel adjacent the other side wall, the physical gasket being of an expanded and cured material; the physical gasket is adhered to the channel and to the electromagnetic gasket; and the electro-magnetic and physical gaskets are in compression between the side walls of the channel.

9. A gasketted housing component as claimed in claim 8, wherein the channel has a first deeper channel portion in which the electromagnetic gasket is disposed and a second shallower channel portion in which the physical gasket is disposed.

10. A gasketted housing component as claimed in claim 8 or 9, wherein the electro-magnetic gasket projects further from the channel than the physical gasket.

11. A gasketted housing component as claimed in any of claims 8 to 10, wherein the electro-magnetic gasket is softer than the physical gasket.

12. A gasketted housing component substantially as described with reference to the drawings.

13. A method or gasketted housing component as claimed in any of claims 1 to 6 or 8 to 11, wherein said material is a two-part mix of a first component having Polyol as a major component and a second component having Isocyanate as a major component.

14. A method or gasketted housing component as claimed in any preceding claim, wherein the side walls of the channel are substantially parallel.

15. A method or gasketted housing component as claimed in any of claims 1 to 13, wherein the side walls of the channel diverge in the direction into the channel.

16. A method or gasketted housing component as claimed in any preceding claim, wherein the housing component is a panel, door or pillar.

17. A housing having a gasketted housing component as claimed in any of claims 8 to 16, or a housing component to which a gasket has been applied by a method as claimed in any of claims 1 to 7 or 13 to 16, and a second housing component having a surface against which the electromagnetic and physical gaskets abut.