KEY ASSEMBLY DIAPHRAGM SWITCH ACTUATOR WITH OVERTRAVEL AND FEEL MECHANISMS

• US 3,773,997 A
• Filed: 12/13/1971
• Issued: 11/20/1973
• Est. Priority Date: 12/13/1971
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: Evans Pat E, Meryl E. Miller, Michael Muller
• Inventors: Muller, Michael, Evans, Pat. E., Miller, Meryl E.
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Vanderhye, Robert A.
• Application Number:
  US05/207,142
• Time in Patent Office: 708 Days
• Field of Search: 200/153V,159B,159R,172A,153T,159A,172R,77,160
• US Class Current: 200/517
• CPC Class Codes: B41J 5/12 Construction of key buttons
• CPC Class Codes: B41J 5/16 Mounting or connecting key buttons on or to key levers
• CPC Class Codes: H01H 1/2008 Facilitate mounting or replacing contact bridge and pressure spring on carrier H01H11/0012 takes precedence
• CPC Class Codes: H01H 13/705 characterised by construction, mounting or arrangement of operating parts, e.g. push-buttons or keys
• CPC Class Codes: H01H 2003/028 Rotating knob or lever or tumbler that can be turned or pushed by hand in only one direction, e.g. by making inaccessible one side of a tumbler
• CPC Class Codes: H01H 2215/028 alterable
• CPC Class Codes: H01H 2215/034 Separate snap action
• CPC Class Codes: H01H 2221/026 Guiding or lubricating nylon
• CPC Class Codes: H01H 2221/044 Elastic part on actuator or casing
• CPC Class Codes: H01H 2227/028 Key stroke
• CPC Class Codes: H01H 2227/032 Operating force
• CPC Class Codes: H01H 2229/018 Testing
• CPC Class Codes: H01H 2229/044 Injection moulding
• CPC Class Codes: H01H 2233/02 captured between assembled parts of support
• CPC Class Codes: H01H 2233/058 One degree of freedom
• CPC Class Codes: H01H 2233/086 Inserting
• CPC Class Codes: H01H 2233/096 with limited freedom
• CPC Class Codes: H01H 2235/018 Spring seat

Abstract

A key assembly for actuating a diaphragm switch, and including a housing, a keystem movably mounted on the housing, and a switch actuator coupled to the keystem through a lost-motion connection arranged so a relatively large stroke of the keystem is required to effect a small actuator motion needed to operate the switch. A coil spring biases the keystem away from the housing to an extended position in which the switch is not actuated, and a second coil spring urges the actuator away from the keystem. The lost-motion connection between the keystem and actuator provides positive retraction of the actuator during the return stroke of the keystem. A leaf spring on the keystem rides a cam surface or ramp on the housing, and the ramp is shaped to modify the effect of the coil springs such that the keystem tends to toggle past the point of switch actuation to prevent switch jitter and to provide a tactile signal that actuation has occurred.

Claims

1. A key assembly for actuating a device, comprising:

a housing;

a keystem mounted on the housing to be movable through a stroke between a normally extended position and a depressed position, the keystem having a pair of elongated channels therein, each channel having a lower end defining a stop shoulder;

an actuator mounted on the housing to be movable through a stroke between a normally retracted position and an extended position, the actuator having a pair of arms extending therefrom over opposite sides of the keystem, each arm having an inwardly extending portion fitting into a respective channel to form a lost-motion connection which captively retains the actuator on the keystem;

first resilient means disposed between the keystem and actuator for urging the actuator away from the keystem; and

second resilient means disposed between the housing and keystem for urging the keystem toward the normally extended position;

the keystem and first resilient means being operative to move the actuator toward the extended position when the keystem is moved toward the depressed position, the arm portions being movable in the keystem channels to permit the keystem stroke to exceed the actuator stroke, the arm portions abutting the channel stop shoulders to drive the actuator to the retracted position when the keystem is returned to the normally extended position.

2. The asseMbly defined in claim 1 in which the actuator and keystem are non-rotatively mounted on the housing.

3. The assembly defined in claim 2 and further comprising a third resilient means arranged between the keystem and housing to be operative during an intermediate portion of the keystem stroke to impose on the keystem a force resisting keystem motion followed by an opposite force aiding further keystem motion as the keystem is moved through the intermediate stroke portion toward the depressed position.

4. A key assembly for actuating a diaphragm switch, comprising:

a hollow housing having a lower end adapted for mounting on the switch;

a keystem slidably mounted in and extending from an upper end of the housing, the keystem being movable between a normally extended position and a depressed position;

a first spring disposed between the keystem and housing for urging the keystem toward the extended position, the first spring exerting an increasing restoring force opposing an actuating force exerted on the keystem to move the keystem from the normally extended position toward the depressed position;

a resilient means interposed between the keystem and housing for modifying the total force opposing the actuating force by first increasing the total force and then decreasing the total force as the keystem is moved through an intermediate portion of full downstroke travel toward the depressed position;

an actuator slidably mounted in the housing and having a lower end movable into operative contact with the switch when the housing is mounted on the switch, the actuator having a coupling means extending therefrom in captive engagement with the keystem, the coupling means providing a lost-motion connection which forces the actuator away from the switch into a retracted position when the keystem is in the normally extended position while permitting limited downstroke motion of the keystem toward the depressed position without requiring equal motion of the actuator; and

a second spring disposed between the keystem and actuator to urge the keystem and actuator apart, the second spring providing a resilient connection between the keystem and actuator such that an increasing restoring force exerted by the second spring during the keystem downstroke is effective to urge the actuator away from the keystem into actuating contact with the switch, the second spring permitting overtravel movement of the keystem beyond a position adequate to obtain switch actuation, while maintaining a restoring force against the actuator to hold the switch in an actuated position during overtravel movement and until the keystem is permitted to move back toward the extended position.

5. The assembly defined in claim 4 in which the keystem and actuator are non-rotatively mounted in the housing whereby rotation is prevented as the keystem and actuator are moved linearly with respect to the housing.

6. The assembly defined in claim 5 in which the housing defines a stop surface abutting the actuator in the retracted position to prevent further motion of the actuator toward the upper end of the housing, and to limit upward travel of the keystem with respect to the housing.

7. The assembly defined in claim 4 in which the housing defines a channel extending in the direction of keystem travel, the channel having a projection intermediate its ends extending toward the keystem, and in which the resilient means includes a resilient arm on the keystem and having a follower which fits in and rides along the channel as the keystem is moved in the housing, the follower riding over the channel projection to deflect and then release the resilient arm as the keystem is moved through the intermediate position.

8. The assembly defined in claim 7 in which the keystem has a pair of side surfaces defining channels which are elongated in the direction of keystem motion, each channel having a stop shoulder at a lower end thereof, and in which said coupling means comprises a pair of arMs secured to and extending from the actuator over the side surfaces of the keystem, the arms having inwardly extended ends slidably fitted into the channels and abutting the stop shoulders to limit separation of the keystem and actuator.

9. The assembly defined in claim 8 in which the actuator and arms are integrally formed from a material having sufficient resiliency that the arms may be spread apart to slide over the keystem and then resume a normal spacing with the inwardly extending ends of the arms captively engaged in the keystem channels.

10. The assembly defined in claim 4 in which the keystem includes a cap post, the post having projections extending therefrom, and further comprising a cap having a socket and formed of a plastic material which will cold flow, the post making a force fit in the socket, the cap being formed of a softer material than a material forming the keystem post whereby the cap will cold flow around the post projections to form detent sockets receiving the projections and retaining the cap on the post.

11. A key assembly comprising:

a diaphragm switch having an actuating surface which is movable to effect switch actuation;

a hollow housing having an undersurface disposed adjacent the switch actuating surface;

a clamping means securing the switch and housing together;

a keystem slidably mounted in and extending from an upper end of the housing, the keystem being movable toward and away from the switch actuating surface between a depressed position and a normally extended position, the keystem having a pair of side surfaces defining channels which are elongated in the direction of keystem motion, each channel having a stop shoulder at a lower end thereof;

a first coil spring disposed between the keystem and housing for urging the keystem toward the extended position;

an actuator slidably mounted in the housing between the keystem and switch actuating surface, the actuator having a pair of arms secured to and extending therefrom over the keystem side surfaces in captive engagement of the keystem, the arms having inwardly extending ends slidably fitted in the keystem channels and abutting the stop shoulders to limit separation of the keystem and actuator, the arms thereby forming a lost-motion connection which pulls the actuator in a direction away from the switch actuating surface into a retracted position when the keystem is in the normally extended position while permitting limited downstroke keystem motion toward the depressed position without requiring equal motion of the actuator; and

a second spring disposed between the keystem and actuator to urge the keystem and actuator apart, the second spring providing a resilient connection between the keystem and actuator such that an increasing restoring force exerted by the second spring during a keystem downstroke toward the depressed position is effective to urge the actuator away from the keystem against the switch actuating surface to effect switch actuation, the second spring permitting overtravel movement of the keystem beyond a position adequate to obtain switch operation, while maintaining a restoring force against the actuator to hold the switch in an actuated position during overtravel movement and until the keystem is permitted to move back toward the extended position.

12. The assembly defined in claim 11 in which the actuator and arms are integrally formed from a material having sufficient resiliency that the arms may be spread apart to slide over the keystem and then resume a normal spacing with the inwardly extending ends of the arms captively engaged in the keystem channels.

13. The assembly defined in claim 12 in which the keystem and actuator are non-rotatively mounted in the housing, and in which the housing defines a sto surface abutting the actuator in the retracted position to prevent further motion of the actuator toward the upper end of the housing, and to limit upward travel of the keystem with respect to the hoUsing.

14. The assembly defined in claim 13 in which the housing defines a channel extending in the direction of keystem travel, the channel having a projection intermediate its ends and extending toward the keystem, and in which the keystem includes an integrally formed spring arm having a follower which fits in and rides along the channel as the keystem is moved in the housing, the follower riding over the channel projection to deflect and then release the spring arm as the keystem is moved through an intermediate downstroke position to effect switch operation.