Push buttons

• US 4,540,865 A
• Filed: 02/29/1984
• Issued: 09/10/1985
• Est. Priority Date: 03/01/1983
• Status: Expired due to Fees

• Current Assignee: GEC Plessey Telecommunications Limited
• Original Assignee: Plessey Overseas Limited (Marconi Holdings Company Limited)
• Inventors: Calder, John
• Primary Examiner(s): Shepperd, John W.
• Application Number:
  US06/584,626
• Time in Patent Office: 559 Days
• Field of Search: 200/159 B, 200/340, 200/302.2, 200/5 A
• US Class Current: 200/512
• 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 2209/006 Force isolators
• CPC Class Codes: H01H 2215/006 Only mechanical function
• CPC Class Codes: H01H 2215/008 Part of substrate or membrane
• CPC Class Codes: H01H 2221/024 Transmission element
• CPC Class Codes: H01H 2223/024 Screw
• CPC Class Codes: H01H 2227/022 Collapsable dome

Abstract

A keyboard (61) is provided with rubber (silicone) buttons (64, 66) with collapsible webs (14) connecting the buttons to a base layer (10, 40, 60). A solid finger of rubber (20) underneath each button actuates a membrane switch (23) underneath the button. Additionally or alternatively a conductive member (52) can be attached to the end of the finger (20) to make two contacts (48, 50, 56, 58). The buttons and the finger can be of any suitable section, such as round, rectangular etc., and a variety of types of membrane switches can be used.

Claims

1. A push button device, comprising:

a moulded resilient body;

a substantially flat base member having electrical contacts, said moulded resilient body and base member forming a sealed hollow enclosure; and

a guide plate having at least one opening therein, said moulded resilient body partially protruding through the opening in said guide plate;

said moulded resilient body comprising an inner flat base portion attached and parallel to said base member, a side wall portion which includes an arcuate deformable portion of essentially quarter-circle configuration in cross-section, and a substantially rigid guide portion which partially protrudes through the opening in said guide plate;

said moulded resilient body further comprising a substantially flat outer cover portion extending parallel to the base portion, and a tapered projection having a resilient deformable tip;

said flat base portion of said moulded resilient body being integral with an inner end of said arcuate deformable wall portion in a substantially perpendicular relationship, said substantially rigid guide wall portion being substantially perpendicular to said base member and to an outer end of said arcuate deformable wall portion and having an inner end integral with the outer end of said arcuate deformable wall portion, said cover portion being substantially parallel to the base portion and integral with an outer end of said rigid guide wall portion, said tapered projection being integral with said cover portion and projecting from substantially an entire internal surface area of said cover portion to present a reduced inner tip surface area extending parallel to said base member, with said reduced inner surface area being located over said base member electrical contacts,

said guide plate being shaped and mounted to restrict movement of the base portion of said moulded resilient body relative to said base member; and

said moulded resilient body arcuate deformable wall portion deforming when a load is applied to said cover portion, causing substantially perpendicular movement of said tapered projection toward said base member and a two-stage deformation of tactile response by said arcuate deforming wall portion, said tapered projection after the second stage of deformation causing electrical connection between said base member contacts but having sufficient deformability in its tip to prevent excessive load being applied to said base member and causing damage thereto.

2. A push button device as claimed in claim 1, in which a stop portion is formed on the inner end of the rigid guide portion adjacent to the connection between the guide portion and the arcuate deformable portion and extends beyond the connection toward said base member, the stop portion contacting a surface of said base member when the end of the projection distorts in shape against the surface, to prevent overtilting of the push button relative to said guide plate.

3. A push button device as claimed in claim 1, in which said arcuate deformable sidewall portion of said moulded resilient body is substantially thinner than said rigid guide wall portion so as to be comparatively flexible with respect to said rigid guide portion.

4. A push button device as claimed in claim 1, in which support webs extend from said base portion of said moulded resilient body to support said guide plate on said base portion.

5. An assembly of push buttons which extends in two dimensions in the form of a keyboard, comprising:

a moulded resilient mat;

a guide plate with a plurality of openings therein; and

a base plate having a plurality of sets of electrical contacts;

said moulded resilient mat having a plurality of moulded structures each comprising a two-part sidewall which includes an arcuate deformable part of substantially quarter-circle configuration in cross-section, and a substantially rigid guide part;

each of said moulded structures also including an outer cover portion and a tapering projection facing inward from said cover portion, and said moulded resilient mat also having an area of flat resilient material between each moulded structure;

said sidewall arcuate deformable part of each moulded structure having opposite ends integral with and perpendicular to said flat resilient material and said sidewall rigid guide part, respectively, said rigid guide part also being integral with and perpendicular to said cover portion, and said projection being integral with said cover portion and tapering from substantially the entire internal surface of said cover portion to provide a reduced inner surface adjacent said base plate;

said rigid guide portions of said moulded structures projecting through respective ones of the openings in said guide plate and said tapered projection being located over respective sets of said electrical contacts on said base plate; and

said guide plate, moulded resilient mat and base plate forming a sandwich with said guide plate at the top, said moulded resilient mat in the middle and said base plate at the bottom.

6. An assembly as claimed in claim 5, in which said arcuate deformable sidewall portion of each of said moulded structures is substantially thinner than said rigid guide portion of said moulded structure so as to be comparatively flexible with respect to said rigid guide portion.

7. An assembly as claimed in claim 5, in which support webs extend from said moulded resilient mat between said moulded structures to support said guide plate on said moulded resilient mat.