US3729608A

US3729608A - Electrical switch having pivoted arm contact

Info

Publication number: US3729608A
Application number: US00180679A
Authority: US
Inventors: D Wiktor
Original assignee: Automatic Switch Co
Current assignee: Automatic Switch Co
Priority date: 1971-09-15
Filing date: 1971-09-15
Publication date: 1973-04-24
Anticipated expiration: 1990-04-24
Also published as: GB1359072A; FR2152960B1; DE2237771A1; JPS4837661A; FR2152960A1; CA965465A; NL7211436A

Abstract

A switch having relatively movable contacts, one of the contacts including a support member and an arm pivoted to the support member and engageable with the other contact. The other contact is preferably a roller rotatable about an axis extending across the path of movement between the contacts, the roller being engaged by the pivoted arm when the switch closes. A spring urges the arm toward the roller. The arm and the support member form a looped path for electric current so that magnetic force created by the flow of current urges the arm toward the roller. The relatively movable contacts may be arcing contacts of a switch having main relatively movable contacts.

Description

United States Patent 1 1 Wiktor 1451 Apr. 24, 1973 {5 1 ELECTRICAL SWITCH HAVING 3,158,721 l1/1964 Delaney ..200 170 R x PIVOTED ARM CONTACT Primary ExaminerRobert K. Schaefer [75] Inventor. Donnmk M. Wlktor, Cranford, NJ. Assistant Examiner wmiam J. Smith [73] Assignee: Automatic Switch Company, Flor- Attorney Breitenfeld & Levine ham Park, NJ. [22] Filed: Sept. 15, 1971 [57] ABSTRACT Appl. No.: 180,679

US. Cl. ..200/l70 R, 200/166 BB A switch having relatively movable contacts, one of the contacts including a support member and an arm pivoted to the support member and engageable with the other contact. The other contact is preferably a roller rotatable about an axis extending across the path of movement between the contacts, the roller being engaged by the pivoted arm when the switch closes. A spring urges the arm toward the roller. The arm and the support member form a looped path for electric current so that magnetic force created by the flow of current urges the arm toward the roller. The relatively movable contacts may be arcing contacts of a switch having main relatively movable contacts.

12 Claims, 4 Drawing Figures Patented April 24, 1973 2 Sheets-Sheet l INVENTOR.

.oaM/A/ur M. w/xrrm Wrap/145% Patented April 24, 1973 '2 Sheets-Sheet 2 ELECTRICAL SWITCH HAVING PIVOTED ARM CONTACT This invention relates to electrical switches, and more particularly such a switch adapted to close, when, at the instant of closure, a high current flows in the circuit being completed by the switch.

When a switch closes to complete an electrical circuit, the current flowing through the switch contacts and the parts which support them produces a magnetic repulsive force tending to separate the contacts. The magnitude of this repulsive force is a function of the current value involved, and hence high currents produce very large repulsive forces.

Certain types of switching devices, such as safety switches, contactors, circuit breakers, and interrupters, must be designed to close not only when normal current flow is present, but also on occasion when an abnormally high current is flowing, such as happens when the circuit is heavily overloaded, or when a fault current, such as a high in-rush current or short circuit current, is present. On such occasions the magnetic repulsive force tending to separate the contacts as they close is very large, and hence the mechanism associated with the switch must be made powerful enough to overcome the repulsive force and insure that the switch closes and remains closed.

Switching devices of the type mentioned above most commonly employ butt-type contacts which are especially susceptible to the repulsive force mentioned above, and which furthermore have a tendency to bounce and separate when they make contact. Therefore, the switch closing mechanism must be designed to overcome both this bounce and the highest repulsive force the switch is likely to encounter. Some switches employ knife-type contacts in which a blade moves between two contact fingers spring biased toward each other so to tightly squeeze the blade between them. Knife-type contacts, although they bounce less on closing, do present a frictional drag between the closing contacts which must be overcome by the closing mechanism of the switch.

It will be appreciated therefore that switch closing mechanisms must be designed with a large amount of available energy even though all this energy may be needed only on occasion. This over design is not only costly, but it also introduces excessive wear on all associated parts of the switch, since the full available energy of the closing mechanism is used to close the switch each time it operates, whether or not an abnormally large repulsive force is present. It is difficult to reduce the portion of the closing mechanism energy needed to overcome the repulsive force since the force occurs inherently as a result of the current flowing through the switch.

However, it is an object of the present invention to reduce that portion of the closing mechanism energy needed to overcome the reaction of the switch contacts when they engage each other.

It is another object of the invention to provide a switch having butt-type contacts which have little or no tendency to bounce on contact, and in which the magnetic force created by electric current flowing through the contacts is utilized to help urge the contacts toward each other.

Additional objects and features of the invention will be apparent from the following description in which reference is made to the accompanying drawings.

In the drawings:

FIG. 1 is a top plan view of an electrical switch according to the present invention;

FIG. 2 is a vertical cross-sectional view taken along line 22 ofFIG. 1;

FIG. 3 is a fragmentary horizontal cross-sectional view taken along line 33 of FIG. 2; and v FIG. 4 is a fragmentary view, on an enlarged scale, of a portion of FIG. 2 showing the switch immediately after it opens.

The electrical switch chosen to illustrate the present invention is carried by a base 10 of insulation material. Mounted on the upper face of base 10, by bolts 11, are a bus bar 12 and a post 13, the latter being formed of two appropriately bent metal strips. Secured to the upper end of post 13 is a stationary main contact 14. Another bus bar 15 is secured beneath base 10 by bolt 16. When the switch is closed, it electrically connects bus bars 12 and 15, and when the switch is open it disconnects these two bus bars.

Secured to post 13 by screw 19 is a frame 20 formed of a single bent piece of metal. The central portion of frame 20 lies against post 13, and a wall 21 extends upwardly from each side of the central portion. Along the upper edge of each wall 21, the metal is bent to define a top 22. The edge 23 of each wall 21 extends upwardly and outwardly from the switch. Secured between the two walls 21 is a pin 24 carrying a rotatable metal roller 25. Roller 25 serves as the stationary arcing contact of the switch.

Projecting upwardly from base 10 are two spacedapart supports 28 each of which carries a pivot plate 29, the pivot connection in each case being by means of a pin 30. Plates 29 are shown positioned so that the illustrated switch is closed in FIGS. 1 and 2. When plates 29 are pivoted in a counterclockwise direction in FIG. 2, the illustrated switch opens. For the sake of convenience, the mechanism for pivoting plates 29 is not illustrated.

Mounted on plates 29 is an insulation block 32 which carries a metal bar 33. Fixed to bar 33 is the movable main contact 34 of the switch. Bar 33 is resiliently mounted on block 32, and for this purpose a bolt 35 extends upwardly through block 32 and through an elongated opening 36 in bar 33. Above bar 33, a compression spring 37 surrounds bolt 35 and seats against a pair of washers 38. Spring 37 constantly urges bar 33 downwardly, and thereby provides resilient contact pressure between main contacts 34 and 14. Another screw 39 extends through an opening in bar 33 and into block 32. The lower end of screw 39 fits loosely in block 32 so as to permit some pivotal movement of bar 33 in a vertical plane. Screw 39 serves to secure a metal eyelet 42 to bar 33, and a similar eyelet 43 is secured to bus bar 15 by bolt 16. A flexible electrical connector 44 connects eyelets 42 and 43. Thus, it may be seen that movable main contact 34 is always electrically connected to bus bar 15 through bar 33, eyelet 42, connector 44, eyelet 43, and bolt 16.

The switch chosen to illustrate this invention is of the double-throw variety. Consequently, plates 29 carry a second insulation block 45 carrying a metal bar 46 identical to bar 33. For convenience, only a part of bar 46 is illustrated. However, bar 46 is mounted in the same way as bar 33, and carries all the same components carried by bar 33. In addition, it cooperates with a stationary contact structure (not shown) identical to that described above. A pair of eyelets 47 joined by a flexible electrical connector 48 electrically connect bar 46 to bus bar 15. v

Secured to the upper face of bar 33, by screws 51, is an L-shaped support member 52 having a channelshaped cross-section. The upper end of upstanding leg 53 of support member 52 is shaped to define a pair of cars 54 between which a pivot pin 55 extends. Pivotally mounted on pin 55 is an arm 56 carrying a movable arcing contact 57 at its lower end. Arcing contact 57 is adapted to engage roller 25. Since movable arcing contact 57 moves in a vertical plane, as illustrated in FIG. 2, into and out of engagement with roller 25, the axis of rotation of roller 25 is horizontal and across the path of movement of contact 57. consequently, as arcing contact 57 engages roller 25 and continues its movement, roller 25 rotates thereby greatly diminishing frictional drag between the arcing contacts 57 and 25. Furthermore, due to rotation of roller 25, arcing contact 57 strikes different points on the. surface of the roller, and as a result the useful life of roller contact 25 is greatly increased.

It will be seen that arm 56 can swing toward and away from contact roller 25, and in the present example this is accomplished by arranging pivot pin 55 parallel to pin 24 which carriers roller 55. A compression spring 60 constantly urges arm 56 in a counterclockwise direction, as viewed in FIGS. 2 and 4, so that movable arcing contact 57 is constantly urged toward stationary arcing contact 25. Spring 60 is located within an insulated cup 61 mounted in support member 52. An abutment 62 integral with arm 56 limits the counterclockwise movement of arm 56 by abutting the central web of support member 52, as shown in FIG. 4.

When the switch is in the position shown in FIG. 2 and is to be opened, plates 29 are pivoted in a counterclockwise direction. Main contacts 34 and 14 separate first, after which arcing contacts 57 and 25 separate. Upon separation of the arcing contacts, as indicated in FIG. 4, the are 63 drawn between the contacts tends to move toward the right in FIG. 4, due to the magnetic field associated with the current flowing through the arc. Thus, the arc runs from roller 25 to edges 23 of walls 21, and then out along edges 23. Since edges 23 and arm 56 diverge in the direction of arc movement, the length of the arc increases rapidly which of course helps to extinguish it. An arc chute or chamber (not shown) may surround the arcing contacts to help quench the are.

When plates 29 are thereafter pivoted in a clockwise directionin FIG. 2 so as to close the switch, movable arcing contact 57 first engages roller 25, after which main movable contact 34 engages main stationary contact 14. When contact 57 first meets roller 25, there is little or no contact bounce since contact 57 simply rolls along contact 25. Furthermore, good contact pressure between contacts 57 and 25 is assured in two ways. First, spring 60 provides some of this pressure. In addi tion, before the main contacts close, current flowing between frame and bar 33 flows through arm 56 and leg 53 of support member 52. Since the current flows in opposite direction through arm 56 and leg 53, a magnetic repulsion force is produced tending to swing arm 56 away from leg 53.

Although the arm 56 and roller 25 have been described in the present example in connection with arcing contacts, this arrangement can be used with any switch contacts, including the main contacts. Furthermore, while in the present illustration arm 56 forms part of a movable contact and roller 25 the stationary contact, obviously this arrangement can be reversed. Although a single phase switch is illustrated in the drawings, it is to be understood that block 32 may carry additional poles when required. Each such pole is identical to the one illustrated.

The invention has been shown and described in preferred form only, and by way of example, and many variations may be made in the invention which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to any specific form or embodiment except insofar as such limitations are included in the appended claims.

What is claimed is 1. An electrical switch including first and second relatively movable contacts, said first contact including a support member movable with respect to said second contact, an arm pivotally mounted on said support member and engageable with said second contact, aligned holes in said support and arm, and a pin arranged in said holes, said pin defining a pivot axis fixed with respect to each of said support and arm, whereby the arm is pivotally connected to the support member,

' the pivot axis being so arranged that as said arm swings about said axis it moves in a direction toward and away from said second contact.

2. An electrical switch as defined in claim 1 wherein said contacts include a movable contact and a stationary contact, and said arm forms part of said movable contact.

3. An electrical switch as defined in claim 1 wherein said pivot axis is perpendicular. to the direction of movement between said contacts.

4. An electrical switch as defined in claiin 1 wherein said second contact includes a roller rotatable about an axis extending across the path of movement between said contacts.

5. An electrical switch as defined in claim 4 wherein said pivot axis and said roller axis are parallel.

6. An electrical switch as defined in claini 1 including resilient means urging said arm about its pivot axis toward said second contact.

7. An electrical switch as defined in claim 6 including abutment means for limiting the movement of said arm under the influence of said spring. 1

8. An electrical switch as defined in claim 1 wherein said arm and support member extend generally parallel to each other from said pivot axis, to define a looped path for electrical current flow, and said arm is located between said second contact and said support member when said contacts close, whereby when current flows through the switch the magnetic force created thereby urges said arm away from said support and against said second contact.

S. An electrical switch as defined in claim 1 wherein said relatively movable contacts are arcing contacts,

and the switch includes relatively movable main contacts, said support member being fixed to one of said main contacts and said second contact being fixed to the other of said main contacts.

10. An electrical switch as defined in claim 1 including an electrically conductive element alongside said second contact, an edge of said element diverging from said arm when said switch is closed and extending beyond said second Contact in the direction of divergence, whereby an are drawn between said contacts when the switch opens will jump from said second contact to said edge and lengthen as said switch continues to open.

11. An electrical switch including first and second relatively movable contacts, said first contact including a support member movable with respect to said second contact, said second contact including a roller rotatable about an axis extending across the path of movement between said contacts, and an arm pivotally mounted on said support member and engageable with said second contact, the pivot axis of said arm being so arranged that as said arm swings about said axis it moves in a direction toward and away from said second Contact.

12. An electrical switch including first and second relatively movable contacts, said first contact including a support member movable with respect to said second contact, and an arm pivotally mounted on said support member and engageable with said second contact, the pivot axis of said arm being so arranged that as said arm swings about said axis it moves in a direction toward and away from said second contact, and an electrically conductive element alongside said second contact, an edge of said element diverging from said arm when said switch is closed and extending beyond said second contact in the direction of divergence, whereby an are drawn between said contacts when the switch opens will jump from said second contact to saidedge and lengthenas said switch continues to open.

Claims

1. An electrical switch including first and second relatively movable contacts, said first contact including a support member movable with respect to said second contact, an arm pivotally mounted on said support member and engageable with said second contact, aligned holes in said support and arm, and a pin arranged in said holes, said pin defining a pivot axis fixed with respect to each of said support and arm, whereby the arm is pivotally connected to the support member, the pivot axis being so arranged that as said arm swings about said axis it moves in a direction toward and away from said second contact.

3. An electrical switch as defined in claim 1 wherein said pivot axis is perpendicular to the direction of movement between said contacts.

4. An electrical switch as defined in claim 1 wherein said second contact includes a roller rotatable about an axis extending across the path of movement between said contacts.

6. An electrical switch as defined in claim 1 including resilient means urging said arm about its pivot axis toward said second contact.

7. An electrical switch as defined in claim 6 including abutment means for limiting the movement of said arm under the influence of said spring.

9. An electrical switch as defined in claim 1 wherein said relatively movable contacts are arcing contacts, and the switch includes relatively movable main contacts, said support member being fixed to one of said main contacts and said second contact being fixed to the other of said main contacts.

10. An electrical switch as defined in claim 1 including an electrically conductive element alongside said second contact, an edge of said element diverging from said arm when said switch is closed and extending beyond said second contact in the direction of divergence, whereby an arc drawn between said contacts when the switch opens will jump from said second contact to said edge and lengthen as said switch continues to open.

12. An electrical switch including first and second relatively movable contacts, said first contact including a support member movable with respect to said second contact, and an arm pivotally mounted on said support member and engageable with said second contact, the pivot axis of said arm being so arranged that as said arm swings about said axis it moves in a direction toward and away from said second contact, and an electrically conductive element alongside said second contact, an edge of said element diverging from said arm when said switch is closed and extending beyoNd said second contact in the direction of divergence, whereby an arc drawn between said contacts when the switch opens will jump from said second contact to said edge and lengthen as said switch continues to open.