Laminate switch assembly having improved durability

• US 4,423,294 A
• Filed: 06/17/1982
• Issued: 12/27/1983
• Est. Priority Date: 06/17/1982
• Status: Expired due to Fees

• Current Assignee: Hall & Company Limited (Ferguson Plc)
• Original Assignee: Hall & Company Limited (Ferguson Plc)
• Inventors: Walser, Richard J., Wyant, Gary M.
• Primary Examiner(s): Goldberg, E. A.
• Assistant Examiner(s): Ginsburg, Morris
• Application Number:
  US06/389,527
• Time in Patent Office: 558 Days
• Field of Search: 200/5 A, 200/159 B, 200/292
• US Class Current: 200/5.00A
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 2203/02 Interspersed fingers
• CPC Class Codes: H01H 2209/006 Force isolators
• CPC Class Codes: H01H 2213/01 with internal pressure of other switch sites
• CPC Class Codes: H01H 2215/006 Only mechanical function
• CPC Class Codes: H01H 2215/022 Asymmetric; Elliptic; Square

Abstract

A laminate switch assembly or keyboard comprises a tensioned dome switch plate having improved durability which provides tactile feedback to the operator. Each tensioned dome on the switch plate is aligned with an electrical contact area formed on a printed circuit board so that depression of the dome completes an electrical circuit through the aligned contact area. Each tensioned dome is surrounded by a reinforcing collar or band which relieves the stresses normally produced in the transition area between the switch domes and the remaining planar portion of the switch plate.

Claims

1. A laminate switch assembly comprising:

a printed circuit board having at least one pair of electrical contact areas formed thereon;

a tactile dome switch plate having a tensioned tactile dome aligned with each pair of said at least one pair of electrical contact areas on said circuit board and a reinforcing band encircling each tactile dome; and

contact means interposed between said circuit board and said switch plate for interconnecting an aligned pair of contact areas upon depression of an associated tensioned tactile dome whereby an electrical connection is completed through said aligned pair of contact areas by depressing said associated tensioned tactile dome and stresses created in said switch plate between said associated tensioned tactile dome and the remainder of said switch plate due to the flexure of said associated tensioned tactile dome are relieved by said reinforcing band which remains substantially stationary compared to the movement of said tactile dome upon depression and release of said associated tensioned tactile dome.

2. The laminate switch assembly of claim 1 wherein said contact means comprises an electrically conductive coating on the interior surface of said associated tenionsed tactile dome.

3. The laminate switch assembly of claim 1 wherein said tensioned tactile dome and said reinforcing band are approximately equal in thickness and are formed into said switch plate.

4. The laminate switch assembly of claim 3 wherein said switch plate is formed of a thermoplastic material.

5. The laminate switch assembly of claim 4 wherein a key designation is formed into said tensioned tactile dome and said reinforcing band is formed of a contrasting color whereby a permanent key designation and a pleasing appearance can be imparted to said laminate switch assembly.

6. A laminate switch assembly comprising:

a printed circuit board having a plurality of intermeshed pairs of electrical contact areas formed thereon;

a first electrically insulating spacer covering said circuit board and including apertures therethrough aligned with each of said pairs of electrical contact areas;

an electrically insulating contact sheet having electrically conducting pads corresponding in number to said pairs of electrical contact areas and positioned on the underside of said sheet in alignment with said apertures so that said pads are positioned opposite to but spaced apart from said electrical contact areas by said first spacer;

a second electrically insulating spacer covering said contact sheet and including apertures therethrough aligned with each pair of said electrical contact areas; and

a tactile dome switch plate covering said second electrically insulating spacer and having tensioned switch domes formed into an otherwise substantially planar plate, said tensioned switch domes being aligned with said pairs of electrical contact areas and having reinforcing collars completely surrounding them, said reinforcing collars remaining substantially stationary during flexing movement of said tensioned switch domes to operate said laminate switch assembly whereby stresses in the transition area between said tensioned switch domes and the planar portion of said switch plate are relieved.

7. The laminate switch assembly of claim 6 wherein said reinforcing collars comprise raised circular rings concentric with said switch domes.

8. The laminate switch assembly of claim 6 or 7 wherein said switch domes extend above said reinforcing collars.

9. The laminate switch assembly of claim 8 wherein said tactile dome switch plate including said switch domes and said reinforcing collars are formed of approximately equal thickness thermoplastic.

10. The laminate switch assembly of claim 9 wherein said reinforcing collars are upwardly arched.