US3676629A

US3676629A - Switch construction with non-bounce contacts

Info

Publication number: US3676629A
Application number: US131160A
Authority: US
Inventors: David Maurice Evans; Roy Theodore
Original assignee: S&C Electric Co
Current assignee: S&C Electric Co
Priority date: 1971-04-05
Filing date: 1971-04-05
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11
Also published as: GB1371422A; CA924365A; AU4063672A

Abstract

The switch blade is pivoted at high speed into and out of engagement with spring biased contacts having contact surfaces of large radius. The mass of the contacts and the spring forces applied thereto are so related to the velocity of the switch blade that bouncing of the contacts is minimized and the circuit is completed so rapidly that arcing is also minimized with normal current flowing only after actual engagement of the contacts by the switch blade. The contacts are mounted at the offset distal ends of relatively rigid contact plates which are secured to opposite sides of a terminal bracket. L-shaped springs bias the contact plates and contacts into engagement with the switch blade. An equalizer extends through the springs and contact plates and through an insulating support bracket that carries a spacing pin to limit movement of the contacts toward each other. The contact assembly is enclosed in an insulating arc extinguishing housing.

Description

United States Patent [151 3,676,629

Evans et al. 1 July 11, 1972 s41 SWITCH CONSTRUCTION WITH NON- 2,751,411 6/1956 Wills ..200/l66 a BOUNCE CONTACTS Primary Examiner-H. 0. Jones [72] Inventors: David Maurice Evan, Wheeling; Roy

. Riverside both of m. Anome Roben R. Lockwood [73] Assignee: S I; C Electric Company, Chicago, Ill. [57] ABSTRACT [22] Filed: April 5, l97l The switch blade is pivoted at high speed into and out of en- I gagement with spring biased contacts having contact surfaces Appl' of large radius. The mass of the contacts and the spring forces applied thereto are so related to the velocity of the switch [52] [1.8. CI. .100] 166 E, 200/ I66 H blade that bouncing of the contacts is minimized and the cir- [Sl] Int. Cl .Jllllh 1/42, HOlh l/SO cuit is completed so rapidly that arcing is also minimized with I M0! 300/166 I66 |70 normal current flowing only alter actual engagement of the 200/ l 70 162 contacts by the switch blade. The contacts are mounted at the offset distal ends of relatively rigid contact plates which are defences Cm secured to opposite sides of a terminal bracket. L-shaped s springs bias the contact plates and contacts into engagement UNITED STATES PATENTS with the switch blade. An equalizer extends through the 2,760,034 8/1956 Kowalski et al. ...............200ll70 A X rings and contact plates and through an insulating support 3,538,287 ll/l970 Mrenna ..200ll66 E bracket that arries a spacing pin to limit movement of the 7.147 6I1970 "200/156 E contacts toward each other. The contact assembly is enclosed KOWalSkl R in an insulating arc extinguishing housin 3,l82,l45 5/1965 Gonnan ...200/l66 E X 3,38l.l05 4/1968 Mortenson ..200/l66 E X BCIalms, 10 Drawing figures S I ll g s "ll 19 1 ti 5 I 14 S 3 s J0 t s k a a -z f 7 '1! 6'5 i I I! 66 l 6- 1 "6! 7 9. I F J 6 t 1; I J/ j In 6 f 7 4 "l// ////l a N 4 Wm! 4 72 1 z r SWITCH CONSTRUCTION WITI-l NON-BOUNCE CONTACTS This invention is an improvement over the construction disclosed in Lindell et al. U.S. Pat. No. 2,894,l01, issued July 7, 1959. It employs the switch operator disclosed in Bernatt et al. U.S. Pat No. 3,563,102, issued Feb. 16, 1971 and the arc extinguishing housing disclosed in Harner et al. application Ser. No. 104,589, filed Jan. 7, 1971.

Among the objects of this invention are: To provide a switch construction in which a switch blade engages contacts at high speed with minimum of bouncing; to arrange for the switch blade to engage the contacts at a relatively shallow angle; to cause mechanical oscillations of the contacts to cease before the load current flow reaches a substantial portion of its maximum value; to bias the contacts toward each other and to limit the movement thereof to slightly less than the thickness of the switch blade; and to provide auxiliary contact fingers for engagement first and disengagement last by the switch blade in moving to and from the switch closed position.

In the drawings:

FIG. I is a view, in front elevation, of a three phase switch construction in which this invention is embodied.

FIG. 2 is a view in side elevation and taken generally along line 2-2 of FIG. I to show one of the phase switch assemblies.

FIG. 3 is a view, at an enlarged scale, taken generally along line 3-3 of FIG. 1.

FIG. 4 is a detail sectional view, at an enlarged scale, taken generally along line 44 of FIG. 2 and line 4-4 of FIG. 3 to show more clearly the features of the contact construction.

FIG. 5 is a sectional view, at an enlarged scale, taken generally along line 5-5 of FIG. 4 and showing the switch blade approaching the switch closed position.

FIG. 6 is a view, similar to FIG. 5, but showing the switch blade in the switch closed position.

FIG. 7 is a view in side elevation of the stationary contact assembly.

FIG. 8 is a view, similar to FIG. 7, and shows a modified contact construction provided with auxiliary contact fingers.

FIG. 9 is a sectional view, at an enlarged scale, taken generally along line 9-9 of FIG. 8 and shows the switch blade moving toward the switch closed position.

FIG. 10 is a view, similar to FIG. 9, and shows the switch blade in the switch closed position.

In FIGS. 1 and 2 the reference character It) designates, generally, a three phase switch construction. It includes a metallic frame II on which three phase switch assemblies, indicated generally at 12, I3 and 14, are mounted. Each of the phase switch assemblies comprises a switch blade that is secured to a metallic switch blade support plate 16 which is carried by insulators 17 that are mounted to pivot about a horizontal axis 18. Connection to the switch blade support plate 16 is made by a sliding contact 20 which is mounted on and secured to a terminal 21. The terminal 21 is mounted on a lower insulator 22 which is carried by the metallic frame It.

Each phase switch assembly also includes a stationary contact assembly that is indicated, generally, at 25 the details of which will be set forth hereinafter. The contact assembly 25 includes a contact support terminal bracket 29 that is mounted on an upper insulator 30 by bolts 31. The stationary contact assembly 25 is enclosed by an arc extinguishing structure in the form of an insulating arc extinguishing housing that is indicated, generally, at 33. It is secured by bolts 34 to the contact support terminal bracket 29.

For pivoting the switch blades 15 and the insulators 17 between the switch open and the switch closed positions about horizontal axis 18 a crank arm 35 is connected to the pivotable assembly as shown in FIG. 3. An operating link 36 interconnects the crank arm 35 to a crank arm 37 which is arranged to be pivoted by an operator that is indicated, generally, at 38. The operator 38 may be constructed as disclosed in the above Bernatt et al. patent. The construction of the operator 3!! and the linkage driven thereby is such as to pivot the distal end of each of the switch blades 15 at a velocity of the order of 28 to 34 feet per second. One reason for this relatively high velocity is to minimize arcing between the distal end of each switch blade 15 and the associated contact assembly 25 when the circuit is closed to pick up a load or is closed on an overload or short circuit. Since the time permitted for arcing is correspondingly reduced, there is a corresponding reduction in the erosion that otherwise would take place if the circuit were not closed so rapidly.

As shown in FIG. 4, the switch blade I5 is arranged to pivot through a slot 39 in the arc extinguishing housing 33. The slot 39, as described more fully in the l-Iarner et al. application, above referred to, is formed by lelt and right housing plates 40 and 41 which include left and right housing contact cover sections 42 and 43. The stationary contact assembly 25 is located within the cover sections 42 and 43 and also within left and right contact covers 44 and 45.

Each stationary contact assembly 25 includes a pair of contact plates 48 of good conducting metal. They are secured to opposite sides of the contact support terminal bracket 29 by bolts 49. The contact plates 48 have ofi'set distal ends 50 which are provided with ribs 51 along their edges for the pur pose of rigidifying these distal ends 50 in order to maintain more accurately spacing between contacts 52 that are mounted at the distal ends of the offset ends 50. As shown in FIGS. 4-7, the contacts 52 are circular and they have integral extensions 53 that are headed over to mount them securely on the distal ends of the ends 50 of the contact plates 48. The contacts 52 preferably are formed of copper as are the contact plates 48 and the switch blade 15. The contact support terminal 29 may be formed of aluminum.

The circular contacts 52 have contact surfaces 54 which are arranged to engage opposite sides of the switch blade 15 in the switch closed position shown in FIG. 6. Preferably these contact surfaces 54 have a relatively large radius. For example, as indicated in FIG. 4 the radius 55 may be of the order of 3 inches. The switch blade I5 has the edge which approaches the contacts 52 beveled as indicated at 56 so that the engagement of the switch blade 15 with the contacts 52 takes place at a relatively shallow angle. Silver inserts S7 in the opposite sides of the switch blade 15 provide low resistance contact engagernent with the contact surfaces 54.

The ofi'set distal ends 50 of the contact plates 48 and thereby the contacts 52 are biased toward each other and into contact engagement with the silver inserts 57 by L-shaped leaf springs that are indicated, generally, at 60. The leaf springs 60 include long arms 6l which overlie the outer sides of the offset distal ends 50 and have bifurcated distal ends 62, FIG. 7, to receive the headed over extensions 53 and to provide two areas of contact engagement with the adjacent surfaces of the contact plates 48. The leaf springs 60 also include short arms 63 which have bifurcated distal ends 64 that engage the opposite sides of the contact plates 48 intermediate their ends and adjacent the bolts 49.

With a view to maintaining the leaf springs 60 under tension an equalizer in the form of a bolt 65, FIG. 4, extends through the intermediate sections of the long arms 61 and through the offset distal ends 50 of the contact plates 48 and through the contact support terminal bracket 29. The openings through the contact plates 48 and the terminal bracket 29 for the equalizer bolt 65 are clearance openings.

As shown in FIG. 5 a space 66 is provided between the contact surfaces 54. This space is slightly less than the thickness of the switch blade 15 or the distance between the contact surfaces of the silver inserts 57. In order to maintain the space 66 a spacer pin 67, FIG. 4, is employed. The spacer pin 67 may be formed of stainless steel and is held in position by a C-shaped insulating support bracket 68. It will be observed that the support bracket 68 overlies the adjacent portion of the terminal bracket 29 and that the equalizer bolt 65 also extends therethrough. The length of the spacer pin 67 is such that, the the absence of the switch blade 15, the space 66 between the contact surfaces 54 is maintained. When the switch blade 15 is shifted to the position shown in FIG. 6 or to the switch closed position, the contacts 52 are moved slightly apart against the biasing action of the leaf springs 60. At that time the full spring force of the leaf springs 60 is exerted against the contacts S2 to provide corresponding pressure against the silver inserts 57.

In operation the switch blade 15 is pivoted in the direction indicated by arrow 69, FIG. 5, by the spring operator 38 at a velocity of the order of 28 to 34 feet per second. As the switch blade 15 approaches the contacts 52 under such conditions that current flow at relatively high voltage is to be established, there is a tendency for an arc to form between the advancing edge of the switch blade 15 and one or the other of the contacts 52. The time from are initiation to positive contact of the switch blade IS with the contact surfaces 54 is approximately l millisecond if the arc is established at voltage crest. This represents approximately one fourth of the time for the current to reach its maximum value. If the current is established at voltage zero, the time will be less than one third of a millisecond. As pointed out, because of the beveled edge 56 and the large radius of the contact surfaces 54 the contact engagement takes place at a relatively shallow angle. There is further blade travel after the time of positive contact but during this time the contact is a sliding contact and little or no arcing exists. The total time from are initiation until the switch blade 15 reaches the fully closed position shown in FIG. 6 is 4 to 5 milliseconds or approximately one fourth cycle of 60 Hz. The switch, constructed as described, is capable of closing on a high voltage circuit (5,000 volts or more) with a high current available (l0,000 amperes or more). For example the switch construction disclosed herein is capable of closing on a 10,000 ampere fault at Kv three times and still carry rated current of the order of 400 to 600 amperes. Also it is capable of closing on a 20,000 ampere fault at the same voltage twice and still carry the rated current. By mounting the stationary contact assembly 25 within the insulating arc extinguishing housing 33 the violence of fault closing is limited to a level which minimizes damage. Also this construction permits opening the circuit and rapid extinguishment of the arc incident to such action.

An important feature of the present invention is the reduction to a minimum of transient mechanical oscillations incident to the switch closing operation. This is obtained through the use of the leaf springs 60 arranged to apply the proper tension to the contact plates 48 and to the contacts 52 and their mass is so chosen as to achieve this result. There is then a minimum of bouncing of the contacts 52 when the switch blade 15 is pivoted to the switch closed position shown in FIGS. 4 and 6. In the construction of the stationary contact assembly 25, as described, the contacts 52 can move slightly from side to side as a unit. This prevents magnetic forces from causing unbalanced pressure on opposite sides of the switch blade 15. It is for this reason that the two bshaped leaf springs 60 are provided with the equalizer bolt 65 interconnecting them. Since the ribs 51 are provided along the edges of the offset distal ends 50 of the contact plates 48 the deflection of these plates is limited to the area near where they are anchored by the bolts 49 to the contact support terminal bracket 29. Since the contact plates 48 are longer than the leaf springs 60, they cannot apply a large force to the contacts 52. Thus the pressure applied by the contacts 52 to opposite sides of the switch blade 15 is determined solely by the leaf springs 60. Accordingly, change in contact pressure does not occur if the contact plates 48 are bent or annealed.

For the purpose of increasing the life of the contacts that are engaged by the switch blade 15 in the switch closed position, the construction as shown in FIGS. 8-10 can be employed. Here it will be observed that auxiliary contact fingers 71 are secured by rivets 72 to the offset distal ends 50 of the contact plates 48. The auxiliary contact fingers 7| are located between contacts 73 and the contact support terminal bracket 29. Integral extensions 74 from the contact 73 are headed over to secure them to the contact plates 48. Because of the limitations of space the contacts 73 are not circular as are the contacts 52. Rather the contacts 73 have parallel sides 75.

However, their contact surfaces 76 have the same radius as the radius 55 for the contact surfaces 54 of the contacts 52.

in operation, when the switch blade 15 is pivoted in a direction indicated by arrow 77 in FIG. 9, the beveled edge 56 first approaches the extensions of the auxiliary contact fingers 71 which are indicated at 78. Any are that may be established is formed between one or the other of the extensions 78 of the auxiliary contact fingers 71. As a result no arcing takes place between the switch blade 15 and the contacts 73 as the switch blade continues to move to the switch closed position shown in FIG. 10.

We claim:

l. A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contacts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, the mass of said contacts and the forces exerted thereon by said leaf springs related to the velocity at which said contact surfaces are engaged by said switch blade being such that bouncing of said contacts is minimized, and operating means for moving said switch blade into engagement with said contact surfaces at a velocity of the order of 28 to 34 feet per second whereby transient mechanical oscillations of said contacts cease before load current flow is at a substantial portion of its maximum value.

2. The switch according to claim 1 wherein each of said contact surfaces has a relatively large radius and the edge of said switch blade that approaches said contacts is beveled whereby impact therebetween is at a relatively shallow angle.

3. The switch according to claim 2 wherein auxiliary contact fingers on said contact plates are engaged first and disengaged last by said switch blade in moving toward and away from engagement with said contact surfaces.

4. The switch according to claim 3 wherein said auxiliary contact fingers are located between said contact support terminal bracket and said contacts have sides extending generally parallel to said auxiliary contact fingers.

S. A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contacts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, and an insulating support bracket overlying opposite sides of said contact support terminal bracket and holding said spacer means in operative position.

6. The switch according to claim 5 wherein said spacer means is in the form of a pin and extends through said insulating support bracket, and said equalizer is in the form of a tension member and extends through said leaf springs, contact plates and said insulating support bracket.

7 A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contacts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, and spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, said leaf springs being generally ff; UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION met. 3, 7 29 Dated y 972 Inventofls) DAVIQM. EVANS and ROY T. SWANSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Win the title page the last name --SWANSON--- of the second inventor has been omitted.

r 1 'dolumn 2, line 71 after "that," insert in-- Signed and sealed this 17th day of October 1972.

(SEAL) Attost:

EDWARD M. FLETCHER JR. ROBERT GOTTSCHALK Attcsting Officer Commissioner of Patents

Claims

1. A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contaCts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, the mass of said contacts and the forces exerted thereon by said leaf springs related to the velocity at which said contact surfaces are engaged by said switch blade being such that bouncing of said contacts is minimized, and operating means for moving said switch blade into engagement with said contact surfaces at a velocity of the order of 28 to 34 feet per second whereby transient mechanical oscillations of said contacts cease before load current flow is at a substantial portion of its maximum value.

5. A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contacts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, and an insulating support bracket overlying opposite sides of said contact support terminal bracket and holding said spacer means in operative position.

7. A switch comprising, in combination, a switch blade and a relatively movable contact assembly mounted in insulated spaced relation, said contact assembly including a contact support terminal bracket, a pair of elongated contact plates secured at one end to opposite sides of said contact support terminal bracket with the distal ends offset and extending therefrom, said contact plates at their distal ends having contacts with contact surfaces facing each other for receiving said switch blade therebetween, a leaf spring overlying each contact plate for biasing said contacts toward each other and into engagement with said switch blade, an equalizer interconnecting said leaf springs intermediate their ends and maintaining them under tension, and spacer means between said contact plates limiting the extent of movement thereof and of said contacts toward each other, said leaf springs being generally L-shaped with the distal ends of the long arms engaging said distal ends of said contact plates and the distal ends of the short arms engaging said contact plates intermediate the ends thereof.

8. The switch according to claim 7 wherein said distal ends of said long and short arms of said L-shaped leaf springs arE bifurcated and said short arms engage those portions of said contact plates in engagement with said contact support terminal bracket.