US3927288A

US3927288A - Electrical switch having a movable contact rolling between stationary contacts

Info

Publication number: US3927288A
Application number: US328869A
Authority: US
Inventors: Jay Utken; Edgar F Hauenstine
Original assignee: PR Mallory and Co Inc
Current assignee: Duracell Inc USA; Emerson Electric Co
Priority date: 1973-02-01
Filing date: 1973-02-01
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: CA1003881A; JPS49111170A; DE2404906A1

Abstract

A round movable contact is moved into engagement with a pair of stationary contacts such that the movable contact will seat between the stationary contacts and upon continued cycling of the switch the movable contact will tend to deform faces of the stationary contact to provide a self-cleaning contact surface on the movable contact and provide a new seat in the stationary contact as it progresses therethrough.

Description

United States Patent Utken et a1.

1 1 Dec. 16, 1975 1 1 ELECTRICAL SWITCH HAVING A 2,935,585 5/1960 Holcombe 200/166 BB x MOVABLE CONTACT ROLLING BETWEEN 3,001,046 9/1961 Racz et a1. 200/166 BB X 3,032,620 5/1962 Siiberg 200/166 BB X STATIONARY CONTACTS 3,311,717 3/1967 Lace 200/166 BB X [75] Inventors: Jay Utken; Edgar F. Hauenstine,

both of Frankfort, 1nd. Primary ExaminerRobert K. Schaefer [73] Assigneez p. Mallory & hm Assistant ExaminerWi1liam J. Smith Indianapolis Ind Attorney, Agent, or FirmChar1es W. Hoffmann; Robert F. Meyer; Dona1d W. Hanson [22] F11ed: Feb. 1, 1973 r [21] Appl. No.: 328,869 [57] ABSTRACT A round movable contact is moved into engagement 152 US. Cl 200/277; 200/155 R; 200/288 with a p Of Stationary Contacts Such that the [51] Int. Cl. H01h 1/16 able Contact will Seat between the Stationary Contacts [58] Field of Search 200/166 BB, 277; 338/157 and upon continued cycling of the switch the movable 333/158 contact will tend to deform faces of the stationary contact to provide a se1f-cleaning contact surface on [56] References Cit d the movable contact and provide a new seat in the sta- UNITED STATES PATENTS tionary contact as it progresses therethrough.

1,520,847 12/1924 Bartholomew 7. 200/166 BB 6 Claims, 4 Drawing Figures US. Patent Dec. 16, 1975 3,927,288

ELECTRICAL SWlTCI-I HAVING A MOVABLE CONTACT ROLLING BETWEEN STATIONARY CONTACTS This invention relates to electrical switches and more specifically to the type of switches which are accompanied with a snap action mechanism. More particularly, the present invention relates to electrical switches wherein a self-centering movable contact engages a pair of stationary contacts.

Aside from mechanical failure or breakage of such a switch mechanism, its switch life is heavily dependent upon electrical contact life, or more specifically, the life of the contact surfaces which engage one another. For example, with repeated cycling, high inrushes of current, in combination with contact bounce, causes spurious arcing and the contact surfaces are degraded to the point where the switch is no longer functional. Further, severe arcing can result in an early failure of the switch due to the arc jumping to other elements of the switch.

Accordingly, the present invention is concerned with an electrical switch wherein a movable contact engages a pair of stationary contacts and has as one of its objects the provision of a switch having longer contact life.

Another object of the invention is the provision of a switch which provides a nesting action between fixed and movable contacts to substantially eliminate contact bounce.

It is another object of the present invention to provide a pair of stationary contacts positioned in substantially the same plane as the direction of movement of a movable round contact.

Another object of the present invention is to provide an electrical switch with at least a pair of stationary contacts positioned in the path of a movable contact such that the movable contact will roll and engage one of the stationary contacts prior to engaging the second stationary contact.

Yet another object of the present invention is to provide an electrical switch such that a movable contact will engage a pair of stationary contacts in a way to nest the movable contact between the stationary contacts.

Still another object of the present invention is to confine the travel of a round movable contact to an operating area bordered by at least two stationary contacts.

These and other objects will become more apparent from the following description and accompanying drawing wherein:

FIG. 1 is a side elevation of an electrical switch coupled to a volume control with portions broken away for purposes of clarity;

FIG. 2 is a cross-section taken along lines 22 of FIG. 1 and showing the switch in one position of operation;

FIG. 3 is a view similar to FIG. 2 but showing the switch in a second position of operation; and

FIG. 4 is an enlarged view of stationary contacts and movable contacts of the switch after repeated cycling in accordance with the invention.

Generally speaking the objects of the invention are accomplished by providing an electrical switch having a self-centering round movable contact engaging at least a pair of stationary contacts by rolling the round 2 movable contact along one of the stationary contacts with the pair of stationary contacts disposed in spaced angular relationship to each other such that continued rolling of the movable contact causes it to nest between the pair of stationary contacts.

Referring now to the drawings and more specifically to FIGS. 1-3 an electrical switch 10 is illustrated as being attached to a volume control 12. As will become apparent, electrical switch 10 is of a snap acting type switch wherein a movable contact is self-centering due to its movement being initiated through a one point contact. Although the concepts of the invention are not limited thereto, the particular switch illustrated as having a self-centering feature is more particularly described in US. Pat. No. 2,820,864 issued Jan. 21, 1958 to W. K. Newman, et al. Volume control 12 includes a shaft 14 rotationally coupled to a rotor 16 for the purpose of changing a variable resistance (not shown) in the control 12. Rotor 16 is provided with a boss 18 to facilitate actuation of electrical switch 10. In the illustrative embodiment, switch 10 is of the single-pole double-throw type and is provided with a snap actuation means 11. Snap-action means 11 includes a rotatable actuator 22, provided with a pair of legs 20 extending into control 12, spring 30, and a switch actuator blade 28. Boss 18 may be rotated into an interference path with one of the legs 20 to change the position of rotatable actuator 22. Rotatable actuator 22 is positioned in a switch housing 24 and supported in the housing to pivot about pivot post 26. Switch actuator blade 28 is also supported for rotational movement in the housing 24 about post 26. Spring 30 is connected between rotatable actuator 22 and switch actuator blade 28. Rotation of legs 20 through rotor 16 and boss 18 will cause rotation of rotatable actuator 22 in the direction of arrow 22' to compress spring 30 to move one of its ends through an overcenter condition. Spring 30 will thereby be released and impart motion to switch actuator blade 28 in the direction of arrow 28' to rotate it to the position shown in FIG. 3.

Located near the center of switch actuator blade 28 and extending upward from its face 32 is a boss 34 which is provided with a rib 36 extending across its diameter. A movable contact means 38 is provided by a contact ring 40 which floats around boss 34 and is disposed between switch actuator blade 28 and terminal board 42. The cooperation of rib 36 with ring contact 40 provides the self-centering characteristics of the ring contact.

As shown in FIG. 1, a switch housing 24 is closed at one end by an insulative terminal board 42. Insulative terminal board 42 is retained in place by a plurality of tabs 44 which are crimped over the outer face thereof. To provide electrical continuity from the inside of the switch 10 to external circuitry, a plurality of terminals are staked into terminal board 42. Terminal means 46 includes a common terminal 48, having a stationary contact portion 50 located inside housing 24, and

terminals

52 and 56 with their

stationary contacts

54 and 58, respectively, also extending into switch housing 24.

As illustrated in FIGS. 2 and 3 it may be seen that the geometrical location of

terminals

48, 52 and 56, with their

stationary contacts

50, 54 and 58, respectively, are positioned in such a manner that ring contact may be moved from a first position, as illustrated In FIG. 2, to a second position as shown in FIG. 3. A shown,

stationary contacts

54 and 58 are rectangular III shape and are in tandem relation with a space 57 ther= between, and they are also slightly skewed with respect to each other. Stationary contact 50 which is also rectangular is spaced from the two contacts which are in tandem and is substantially in line with space 57. Ring contact 40 is limited in its travel to an area boardered by

stationary contacts

50, 54 and 58. As switch actuator blade 28 moves ring contact 40, by way of rib 36, ring contact 40 rolls along the common stationary contact 50. A sufficient amount of clearance is provided with the present arrangement of the stationary contacts such that a relatively small amount of movement is required by the switch actuator blade 28 to move ring contact 40 from one position to the other.

Since ring contact 40 is moved through a one point contact of the rib 36 so as to be self-centering, it may find its own seat between

stationary contacts

50 and 54 as seen in FIGS. 2 and 3. More specifically,

stationary contacts

50 and 54 are positioned a distance apart from each other sufficient to provide a nesting between the ring and stationary contacts when ring contact 40 is placed between either one of the two. As switch actuator blades 28 moves from the position shown in FIG. 2 to that of FIG. 3, ring contact 40 will remain nested between common stationary contacts 50 and stationary contact 54 to assure that electrical continuity is continued until the rib 36 of the switch actuator blade 28 moves across the central opening 41 of contact ring 40. When rib 36 imparts motion to the ring contact 40 on the opposite side of the ring, contact ring 40 will, as shown in FIG. 3, be nested between

stationary contacts

50 and 58.

The operation of the switch may now be described. Shaft 14 of volume control 12 may be manually rotated so that boss 18 on rotor 16 will impart motion to rotatable actuator 22 of switch by way of legs 20. As rotatable actuator 22 is displaced from a position shown in FIG. 2 to that shown in FIG. 3, compression spring 30 is compressed until rotatable actuator 22 moves it through an over-center condition to allow the spring to be released to displace switch actuator blade 28. When switch actuator blade 28 is displaced from a position as shown in FIG. 2 to that shown in FIG. 3, rib 36 on boss 34 will impart motion to ring contact 40 to move it to a position shown in FIG. 3. As ring contact 40 comes into engagement with

stationary contacts

50 and 58, the one point contact of the rib 36 will allow the ring contact 40 to find its own seat between the contacts. Rotation of shaft 14 in the opposite direction will, in like manner, return contact 40 to the position shown in FIG. 2.

Ring contact 40 will tend to move differently depending upon the position in which the switch is mounted. Should switch 10 be mounted in a position as viewed in FIGS. 2 and 3, ring contact 40 will tend to drop between the

stationary contacts

54 and 58 as it travels from the position shown in FIG. 2 to that shown in FIG. 3. In this particular path of movement, ring contact 40 will make contact with stationary contact 58 prior to seating between

stationary contacts

50 and 58 by rotating into engagement with stationary contact 50. Should switch 10 be mounted in a position inverted from that of FIGS. 2 and 3, ring contact 40, due to gravity, will tend to roll along the common stationary contact 50 to therefore be in contact with stationary contact 50 prior to engagement with stationary contact 58. Ring contact 40 will tend to roll into engagement with stationary contact 58 to become lodged between

stationary contacts

50 and 58. In either event the movable contact will be seated between cooperating stationary contacts.

The contact engagement characteristics of ring contact 40 and

stationary contact

50 and 58 will also apply with respect to

stationary contacts

50 and 54 in substantially the same manner. Upon repeated cycling of the switch 10, the continual impacting of the ring 40 into engagement with the

contacts

50, 58 and 50, 54 will cause the material of the stationary contacts to be displaced.

Stationary contacts

50 and 58 have been arranged to allow for contact surface displacement such that changing of the relative relationship between the movable contact and the stationary contact is minimized.

Reduction of contact bounce is achieved by the relative spacing between

stationary contacts

50 and 58, their angular relationship to each other and their location in relationship to the path of movement of the movable ring contact 40. As movable ring contact 40 rolls into seating engagement between stationary contacts 50-58 or 50-54 it will engage one of the stationary contacts, it pivots about a point of contact with the first stationary contact and upon continued movement of rib 36, pivots into engagement with the second stationary contact. As pivoting occurs, a wiping action between the second engaged stationary contact and movable contact 40 is achieved. Ring contact 40 will engage the second stationary contact at a point about the periphery of ring contact 40 to permit nesting simultaneously with the wiping action to thereby minimize the amount of contact bounce and provide an improved electrical contact.

FIG. 4 illustrates an embodiment of the invention wherein there is only a pair of stationary contacts cooperating with a round movable contact. The actuation of round movable contact 60 is accomplished in substantially the same manner as that for movable contact 40 of FIGS. 2 and 3. When actuated in a predetermined direction, movable contact 60 will roll along contact 62 to become nested between

contacts

62 and 64 and when actuated in an opposite direction, the movable contact will, as shown, become disengaged. FIG. 4 also illustrates the condition of contacts operating in accordance with the invention at the end of over 100,000 cycles of turning 6,100 watt lights on and off. Movable contact 60 has formed a slight pocket 61 in stationary contact 62 with a slight amount of mushrooming taking place at 61. In a manner similar to contact 62, stationary contact 64 has been displaced at 66 to conform with the contours of movable contact 60. Also a small amount of mushrooming material 64' is noted on the top surface of the stationary contact 64. Virtually no build-up of material is realized in area 62" and 64" of

stationary contacts

62 and 64, respectively, which would provide a barrier in front of the movable contact to facilitate bouncing of the movable contact 40. As the ring contact 40 continues to move through the

stationary contacts

62 and 64, continued displacement of material in the path of the movable contact 60 will occur.

What is claimed is:

1. In an electrical switch wherein a self-centering round movable contact engages at least three rectangular shaped stationary contacts, two of said contacts disposed in tandem relationship with a space therebetween, the third contact spaced from said first two contacts and overlapping said space, said contacts further being disposed lengthwise directionally substantially parallel to a path of movement of said movable contact, and means rolling said round movable contact between said stationary contacts.

2. In an electrical switch according to claim 1 wherein said stationary contacts are skewed with respect to each other.

3. An electrical switch comprising:

three rectangular stationary contacts, each having a length, width, and thickness, two of which are dis posed lengthwise end to end with a space therebetween and lying in a plane substantially common to a plane determined by the length and width of said rectangular stationary contact, the third spaced from said first two stationary contacts and overlapping said first named space,

a round movable electrical contact rolling on said third stationary contact in a predetermined direction and subsequently nesting between said third stationary contact and one of said first two stationary contacts, continued cycling of said switch causing said movable contact to roll along a path and form a groove lengthwise in said one stationary electrical contact, and

electrical terminals electrically coupled to said stationary contacts.

4. An electrical switch comprising:

at least one pair of rectangular stationary electrical contacts disposed at an angle to each other,

a movable electrical contact ring, t

means disposed within said contact ring engaging an inner periphery thereof and providing a one-point contact therewith to roll said contact ring lengthwise along one of said stationary contacts in a predetermined direction and subsequently nesting between said stationary contacts, continued cycling of said switch causing said contact ring to roll along a path and form a groove lengthwise in said one stationary contact, and

electrical terminals electrically coupled to said stationary contacts.

5. An electrical switch according to claim 4 wherein there are three of said stationary electrical contacts two of said electrical contacts disposed in a spaced relationship in a substantially common plane, the third contact spaced from said first two contacts and overlapping said first named space.

6. An electrical switch according to claim 4 wherein said means disposed within said contact ring comprises a boss and a rib carried by said boss and extending substantially across the inside diameter of said ring contact.

Claims

3. An electrical switch comprising: three rectangular stationary contacts, each having a length, width, and thickness, two of which are disposed lengthwise end to end with a space therebetween and lying in a plane substantially common to a plane determined by the length and width of said rectangular stationary contact, the third spaced from said first two stationary contacts and overlapping said first named space, a round movable electrical contact rolling on said third stationary contact in a predetermined direction and subsequently nesting between said third stationary contact and one of said first two stationary contacts, continued cycling of said switch causing said movable contact to roll along a path and form a groove lengthwise in said one stationary electrical contact, and electrical terminals electrically coupled to said stationary contacts.

4. An electrical switch comprising: at least one pair of rectangular stationary electrical contacts disposed at an angle to each other, a movable electrical contact ring, means disposed within said contact ring engaging an inner periphery thereof and providing a one-point contact therewith to roll said contact ring lengthwise along one of said stationary contacts in a pre-determined direction and subsequently nesting between said stationary contacts, continued cycling of said switch causing said contact ring to roll along a path and form a groove lengthwise in said one stationary contact, and electrical terminals electrically coupled to said stationary contacts.