US3648003A

US3648003A - Electrical switch having contacts provided with rollers

Info

Publication number: US3648003A
Application number: US111064A
Authority: US
Inventors: Dominik M Wiktor
Original assignee: Automatic Switch Co
Current assignee: Automatic Switch Co
Priority date: 1971-01-29
Filing date: 1971-01-29
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07
Also published as: FR2124684A5; CA930782A; GB1330259A

Abstract

A knife-type electrical switch including a blade contact and a pair of roller contacts between which the blade contact moves when the switch closes. The rollers are rotatable about axes substantially perpendicular to the direction of blade movement between them. The rollers have tapered ends, and the blade edge facing the rollers diverges from the rollers. Each roller is carried by an arm mounted to pivot about a point spaced from the rollers, and spring means constantly urge the arms and hence the rollers toward each other.

Description

D United States Patent [151 3,648,003 Wiktor 51 Mar. 7, 1972 [54] ELECTRICAL SWITCH HAVING CONTACTS PROVIDED WITH 1,740,640 12/1929 Austin ..200/166 BB ROLLERS 1,891,935 12/1932 Lapsley..... ..200/166 BB [72] Inventor: Dominik M. Wiktor, Ctanford, NJ. Primary Examiner-H. 0. Jones [73] Assignee: Automatic Switch Company mmmeyfBreltenfeld Levme [22] Filed: Jan. 29, 1971 [57] ABSTRACT [21] Appl. No.: 111,064 A knife-type electrical switch including a blade contact and a pair of roller contacts between which the blade contact moves when the switch closes. The rollers are rotatable about axes 'g "200/166 efi substantially perpendicular to the direction of blade movement between them. The rollers have tapered ends, and the [58] Field of Search ..200/166 BB, 166 E, 162 blade edge facing the toners diverges from the [ones Each [56] References Cited roller is carried by an arm mounted to pivot about a point spaced from the rollers, and spring means constantly urge the NIT STATES PATENTS arms and hence the rollers toward each other.

l,666,978 I 4/1928 Sachs ..200/ 166 BB 7 Claims, 5 Drawing Figures Patented March 7, 1972 2 Sheets-Sheet 1 FIG.

INVENTOR OOMM/IA M. ll/(7'02 ATTORNEYS FIG. 2

Patented March 7, 1972 3,648,003

2 Sheets-Sheet 2 M/M/Al/K M W/KTUZ MORNEYS ELECTRICAL SWITCH HAVING CONTACTS PROVIDED WITII ROLLERS 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 that 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 knife-type contacts which are subject to greatly reduced frictional drag when they close, as a result of which the available energy of the switch closing mechanism can be reduced.

It is another object of the invention to provide contacts having a larger than usual effective contact surface, whereby the useful life of the contacts is extended.

It is a further object to provide such a switch wherein the contacts are specially shaped to effect more rapid quenching of the arc when the switch opens.

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 side elevational view of the contact assembly portion of a switch according to the present invention, the contacts being shown closed in solid lines and open in broken lines;

FIG. 2 is a top view of the contact assembly;

FIG. 3 is a front elevational view of the contact assembly, partially in cross section, taken along the line 33 of FIG. 1;

FIG. 4 is a fragmentary cross-sectional view of the primary arcing contacts at the instant of contact between them; and

FIG. 5 is a fragmentary side elevational view of the primary arcing contacts immediately after opening.

The switch contact assembly chosen to illustrate the present invention includes a base 10 and a shaft I1 pivotable with respect to the base. Base 10 carries three stationary contacts, namely, a main contact, and primary and secondary arcing contacts. Shaft 11 carries three movable contacts, namely, a main contact, and primary and secondary arcing contacts.

Shaft 11 has a square cross-sectional shape, and mounted on the shaft for rotation with it is a rigid channel-shaped contact arm 12, its cross-sectional shape being best seen in FIG. 3. At one end, contact arm 12 has a depression 13 for accommodating two adjacent sides of shaft 11, and a bracket 14 is furnished having a similar depression for. accommodating the other two adjacent side of shaft 11. Four screws 15 interconnect the end of contact arm 12 with bracket 14 to fix the contact arm to shaft 11. Contact arm 12 carries all three movable contacts of the switch, and the switch includes conventional mechanism (not shown) for rotating shaft 11 to produce movement of the movable contacts for closing and opening of the switch.

Arranged below contact arm 12 is the movable main contact 19. Four externally threaded studs 20 project upwardly from contact 19 through four holes in contact arm 12, these holes being of larger diameter than the studs and being internally threaded. An externally threaded bushing 21 is threadably arranged within each of the four holes in contact arm 12 and surrounds the stud 20 passing through that hole. Above each bushing, a nut 22 is threaded on to each of studs 20, and it is the engagement between the nuts 22 and bushings 21 which support contact 19. By rotating bushings 21, the lower ends of which engage contact 19, the contact can be adjusted toward and away from contact arm 12.

Contact arm 12 is formed with a generally rectangular hole 23 (see FIG. 2) through which a leaf spring 24 passes in a downward and forward direction, the rearward end of the spring being fixed to the upper face of arm 12 by screws 25. Spring 24 applies a downward pressure to the movable secondary arcing contact 26. The latter is arranged within a cutout in the front endof main contact 19, the rear edge of the cutout being indicated at 27 in FIG. 1.

Mounted on the upper face of contact arm 12, at its end, is a finger 31 having an elongated triangular shape when viewed from above, and upturned side edges. A threaded stud 30 projects upwardly from contact arm 12 through a hole in finger 31, this hole being of larger diameter than the stud and being internally threaded. An externally threaded bushing 32 is threadably arranged within the hole in finger 31 and surrounds stud 30. Above bushing 32 a nut 33 is threaded on to stud 30. To the rear of stud 30, a screw 34 passes through an elongated hole in finger 31 and is threaded into contact arm 12. In the region of the hole accommodating screw 34, finger 31 has a downwardly bellied portion 35 engaging the upper surface of contact arm 12. It will be appreciated, therefore, that by rotating bushing 32, the lower end of which engages contact arm 12, the position of finger 31 with respect to arm 12 can be adjusted.

Integral with the free end of finger 31 is the movable primary arcing contact 36. This contact is in the form of a blade having an attenuated lower edge 37 which merges into an upwardly and outwardly extending edge 38;

Base 10 carries a block 42 (FIG. 1) to which the stationary main contact 43 of the switch is secured by fastening means 44. A post 45 is also mounted on base 10, by fastening means 46, in front of block 42. A fin 47 projects rearwardly from post 45 and supports the stationary secondary arcing contact 48 (FIG. 1).

A pair of arms 51 (FIGS. 1 and 3) flank post 45, these arms carrying at their upper ends the stationary primary arcing contacts, which according to the present invention are a pair of rollers 52. Rollers 52 have a cylindrical body portion and a tapered nose, giving them a bulletlike shape. The manner in which each roller 52 is mounted on its respective arm 51 is best shown in FIG. 4. A pin 53 projects forwardly from arm 51 and has a reduced diameter region 54 between its ends. Hollow roller 52 fits over pin 53, for rotation with respect to the pin, and has an annular recess 55 in its inner surface aligned with the reduced diameter portion 54 of pin 53. An elliptically shaped spring clip 56 is arranged between pin 53 and roller 52, the clip portions crossing the minor axis of the clip being accommodated by portion 54, and the clip portions crossing the major axis of the clip being accommodated by recess 55. In this way, clip 56 prevents any substantial relative axial movement between pin 53 and roller 52 without preventing relative rotation between the two.

Near its upper end, post 45 has a hole through which a pin 60 extends, this pin having an enlarged head 61 at one end and a second enlarged head 62 threaded on to its other end. Pin 60 also passes loosely through holes in arms 51. Between each head and its respective arm 51 is a compression spring 63 surrounding pin 60. Springs 63 constantly urge arms 51, and hence rollers 52, toward each other thereby providing good contact pressure between contact blade 36 and rollers 52 when the contact blade is between the rollers.

Spaced below pin 60, post 45 has another hole 64 through which a pin 65 extends, this pin having an enlarged head 66 at one end and a second enlarged head 67 threaded on to its other end. Pin 65 also passes loosely through holes 68 in arms 51. Between each head and its respective arm 51 is a compression spring 69 surrounding pin 65. The region of each arm 51 surrounding hole 68 has an inwardly directed spherical bulge 70 which seats slidably against a spherical depression in each face of post 45, in the region surrounding hole 64. Bulges 70 and springs 69 define a resilient pivot connection which allows arms 51 to swing away from each other, against the force of springs 63, when contact blade 36 enters between rollers 52 and allows springs 63 to swing arms 51 toward each other when contact blade 36 is removed.

The broken lines in FIG. 1 illustrate the open position of the switch contact arrangement. When shaft 11 rotates in clockwise direction in FIG. 1, the switch is brought to its closed position shown in solid lines. During movement, from open to closed position, movable primary arcing contact 36 first engages stationary primary arcing contacts 52. Thereafter, movable secondary arcing contact 26 engages stationary secondary arcing contact 48, following which movable main contact 19 engages stationary main contact 43.

When contact blade 36 first meets rollers 52, as shown in FIG. 4, there is no possibility of contact bounce since the blade smoothly enters between the rollers, this movement being aided by the attenuated edge 37 and the cylindrical shape of the rollers. Furthermore, rollers 52 rotate about their axes, which are parallel to each other and substantially perpendicular to the direction of blade movement, as blade 36 moves downwardly between them. Consequently, there is little frictional drag on the moving contact blade despite the fact that springs 63 and 69 create a large contact pressure between the blade and the rollers. This contact pressure is, by the way, increased as a result of the force of attraction between arms 51, resulting from the magnetic fields engendered by electric current flowing in the same direction through both arms. An additional advantage of this arrangement is that due to rotation of rollers 52, the total contact surfaces of these rollers which engage blade 36 are quite large, thereby considerably increasing the useful life of these contacts.

When shaft 1] rotates in a counterclockwise direction to open the switch, main contacts 19 and 43 break first, followed by secondary arcing contacts 26 and 48, after which

primary arcing contacts

36 and 52 separate. Upon separation, as indicated in FIG. 5, the are 73 drawn between the contacts tends to move toward the right in FIG. 5, due to the magnetic field associated with the current flowing through the arc. Thus, the

- arc runs out along edge 38 and the tapered nose of one or both rollers 52. Since edge 38 and the tapered noses diverge in the direction of arc movement, the length of the arc increases rapidly which of course helps to extinguish it.

It should be mentioned that all conductors associated with the various contacts have been omitted for clarity of illustration. In addition, although the blade and roller contact arrangement has been described in the present example in connection with primary arcing contacts, this arrangement can be used with any switch contacts. Furthermore while in the present illustration the blade contact is the movable contact and the rollers the stationary contact, obviously this arrangement can be reversed.

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 a movable contact and a stationary contact, one of said contacts including a bladelike member, the other of said contacts including a pair of side-byside rollers between which said bladelike member is adapted to move when the switch closes, each of said rollers being generally bullet shaped and having a tapered end, the are drawn between said movable and stationary contacts moving toward the tips of said tapered ends when the switch opens, resilient means urging said rollers toward each other to provide contact pressure between said rollers and said bladelike member when the latter is between said rollers, said rollers being rotatable about parallel axes which are substantially perpendicular to the direction of movement of said bladelike member as it moves between said rollers, whereby when the switch closes said rollers are rotated as said bladelike member moves between them thereby reducing frictional drag between said movable and stationary contacts despite the contact pressure between them.

2. An electrical switch as defined in claim 1 wherein said bladelike member has an edge facing said rollers when the switch is open, at least a portion of said edge being arranged at an acute angle to the axes of rotation of said rollers so that said edge diverges from the tapered ends of said rollers, whereby the are drawn between said movable and stationary contacts when the switch opens lengthens as it moves toward the tips of said rollers and bladelike member.

3. An electrical switch including a movable contact and a stationary contact, one of said contacts including a bladelike member, the other of said contacts including a pair of side-byside rollers between which said bladelike member is adapted to move when the switch closes, resilient means urging said rollers toward each other to provide contact pressure between said rollers and said bladelike member when the latter is between said rollers, said rollers being rotatable about parallel axes which are substantially perpendicular to the direction of movement of said bladelike member as it moves between said rollers, one of said contacts including a pair of arms, each arm carrying one of said rollers, said arms and hence said rollers being movable away from each other against the force of said resilient means, the latter constantly urging said arms and hence said rollers toward each other, a post between said arms, a rounded protrusion on each arm spaced from its respective rollers, said protrusion engaging said post, whereby each of said arms is pivotable about the point of engagement between its protrusion and said post, and additional resilient means urging said protrusions against said post.

4. An electrical switch as defined in claim 3 including depressions in said post within which said protrusions are slidably accommodated.

5. An electrical switch as defined in claim 3 including a hole in each of said arms, said hole extending through said protrusion, pin means extending laterally in opposite directions from said post and passing loosely through said holes, and enlargements on the free ends of said pin means spaced from said arms, and wherein said additional resilient means includes a compression spring surrounding said pin means between each of said enlargements and the one of said arms closer to it.

6. An electrical switch as defined in claim 3 including a hole in each of said arms between its protrusions and its roller, pin means extending laterally in opposite directions from said post and passing slidably through said holes, and enlargements on the free ends of said pin means spaced from said arms, and wherein said resilient means includes a compression spring surrounding said pin means between each of said enlargements and the one of said arms closer to it.

7. An electrical switch as defined in claim 6 including an additional hole in each of said arms, said additional hole extend-

Claims

1. An electrical switch including a movable contact and a stationary contact, one of said contacts including a bladelike member, the other of said contacts including a pair of side-byside rollers between which said bladelike member is adapted to move when the switch closes, each of said rollers being generally bullet shaped and having a tapered end, the arc drawn between said movable and stationary contacts moving toward the tips of said tapered ends when the switch opens, resilient means urging said rollers toward each other to provide contact pressure between said rollers and said bladelike member when the latter is between said rollers, said rollers being rotatable about parallel axes which are substantially perpendicular to the direction of movement of said bladelike member as it moves between said rollers, whereby when the switch closes said rollers are rotated as said bladelike member moves between them thereby reducing frictional drag between said movable and stationary contacts despite the contact pressure between them.

2. An electrical switch as defined in claim 1 wherein said bladelike member has an edge facing said rollers when the switch is open, at least a portion of said edge being arranged at an acute angle to the axes of rotation of said rollers so that said edge diverges from the tapered ends of said rollers, whereby the arc drawn between said movable and stationary contacts when the switch opens lengthens as it moves toward the tips of said rollers and bladelike member.

3. An electrical switch including a movable contact and a stationary contact, one of said contacts including a bladelike member, the other of said contacts including a pair of side-by-side rollers between which said bladelike member is adapted to move when the switch closes, resilient means urging said rollers toward each other to provide contact pressure between said rollers and said bladelike member when the latter is between said rollers, said rollers being rotatable about parallel axes which are substantially perpendicular to the direction of movement of said bladelike member as it moves between said rollers, one of said contacts including a pair of arms, each arm carrying one of said rollers, said arms and hence said rollers being movable away from each other against the force of said resilient means, the latter constantly urging said arms and hence said rollers toward each other, a post between said arms, a rounded protrusion on each arm spaced from its respective rollers, said protrusion engaging said post, whereby each of said arms is pivotable about the point of engagement between its protrusion and said post, and additional resilient means urging said protrusions against said post.

7. An electrical switch as defined in claim 6 including an additional hole in each of said arms, said additional hole extending through said protrusion, additional pin means extending laterally in opposite directions from said post and passing loosely through said additional holes, and additional enlargements on the free ends of said additional pin means spaced from said arms, and wherein said additional resilient means includes a compression spring surrounding said additional pin means between each of said additional enlargements and the one of said arms closer to it.