An Electrical Circuit Interrupting Device

Abstract

An electrical switch including a first switch contact mounted at a point spaced in front of a support, and a second switch contact mounted on the support for movement from an on-position in which it engages the first contact to an off-position in which it is spaced to the rear of the second contact. One of the switch contacts has a quenching chamber connected to it which surrounds the space between the first and second contacts until they are separated by a sufficient distance so that arcing no longer occurs. The mounting means for the second switch contact moves the second contact first in a linear direction away from the first contact and then in a pivotal direction back toward the support.

Description

BACKGROUND OF THE INVENTION

This invention relates to electrical switches for power circuits, and more particularly to a switch having tubular contacts actuated by a lever system.

Most conventional switches for power circuits have pivoted knifelike switching members which are moved away from a contact for a sufficient distance such that sparking can not occur when the switch is in the off-position. Accordingly, the size of the switching cubicle or the enclosed metal switch board is determined by the voltage of the system and the distance by which the knife switches must be moved to prevent sparking.

A resulting drawback is that it is not possible to reduce the size of the switching installations without creating safety hazards. Similar size limitations exist for circuit breakers used for protecting against power surges and other overloads. In the cutoff position for either such electrical switches or circuit breakers there may be a considerable space requirement since the switching blades may be rotated through 180.degree. from an on-position in which it is in contact with the associated switch connection to an off-position in which it lies flat against the board and extends in the opposite direction.

SUMMARY OF THE INVENTION

Among the objects of the present invention is the provision of electrical switches which may occupy relatively small space and, in which the space requirement for the switch contact is not substantially different in either the on or the off position.

Briefly stated, these and other objects of the invention are achieved by providing a means for first moving the tubular switching contact away from the associated electrical contact and then in a pivotal direction to the rear of this contact. One switch contact has a quenching chamber at one end for surrounding the space between the contacts until they are separated by a distance such that arcing can no longer occur. The linkage system for moving the tubular contact includes a member having a cam surface and a bolt which is connected to a guide connected to the tubular contact.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, partially in cross section, of an electrical switch according to the present invention in its off-position.

FIG. 2 is a side view similar to FIG. 1 showing the switch of FIG. 1 in an intermediate position between its on and off-positions.

FIG. 3 is a side view similar to FIG. 1 showing the switch of FIG. 1 in its on-position.

FIG. 4 is a front view of the switch of FIG. 1, with the switch shown in its off-position.

FIG. 5 is a sectional view taken on the line 5--5 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and particularly FIGS. 1-4, an electrical switch according to the present invention includes a support frame 1 formed by side members 40 connected by cross members 42, as shown in FIG. 4, carrying insulators 2 and 3. The upper insulator 2 carries a powerline connection 4 and a stationary electrical contact 5. Stationary contact 5 includes an insulating housing 27 of generally tubular shape and a central electrical contact 26 of cylindrical shape which is coaxial with housing 27, and is electrically connected to the current carrying line connection 4 by a power lead 28. A sleeve 30 of insulating material is located between the housing 27 and the contact 26.

The lower insulator 3 carries at its outer end a bracket 7 rigidly supported by a second power line connection 6. Pivoted to the end of bracket 7 is a housing 9 which is made of insulating material in the form of an elongated tube of generally rectangular cross section. A pin 8 carried by bracket 7 is pivotally connected to the lower end of housing 9. One of the lateral walls of housing 9 has a camming slot 16 formed therein. A roller 31 (FIG. 3) rides in camming slot 16 and is rotatably mounted on a bolt 14 which is in turn connected to a lever 13.

The end of bolt 14 fits within a forked slide guide 17 which is fastened to a movable electrical contact 11. Movable electrical contact 11 includes a lower tubular portion 32 of electrically conductive material having an inner diameter of appropriate shape to engage with the fixed arc contact 26. At its upper end it includes a tubular portion 10 formed of insulating material. This material can be of a type which forms a gas under the influence of the arc.

Portion 10 is coaxial with the contact portion 32, and which serves to form a quenching chamber for quenching the arc formed when contact 26 first separates from contact 32. A flexible current lead 20 connects contact 32 and connection 6.

The electrical contact portion 32 could, if desired, be surrounded by a sleeve of insulating material. The forked slide guide 17 is integral with this sleeve and is preferably also made of insulating material.

The lever 13 which carries the bolt 14 at its free end is pivoted at its opposite end by a shaft 12 to the side members 40 of frame 1. The lever is formed of two links 36a and 36b, shown in FIG. 5, made of a material such as metal selected for its mechanical properties rather than its electrical properties. In order to provide electrical insulation, lever 13 carries a troughlike member 18 having sidewalls 18a which are secured to the lever links 36a and 36b, a bottom wall 18b which connects the two sidewalls, and an end wall 18e, all of the portions of member 18 being of insulating material.

Trough 18 serves two purposes: In the off-position of the switch, the trough receives the parts of the switch contact 11 to which a potential may be applied, and thus serves to insulate these parts either from the ground or from parts at a different electrical potential; in addition it serves as an abutment for the switch contact 11. A padding 19 of elastic material is fixed to the bottom wall 18b near the end wall 18d. This serves to dampen mechanical shocks occurring as the switch contact 11 moves into abutting position. The use of the flexible current lead 20 for making electrical connections between the contact 11 and the line connection 6 prevents any current flow through mechanical pivot joints, which flow might cause charring.

The rotation of lever 13 about its pivot 12 is caused by a rod 23 which is connected to lever 13 by a pivot pin 25 at one of the ends of the rod. The opposite end of rod 23 is pivoted by a pivot pin 24 to a rocker arm 22 which is fixed to a shaft 21. Shaft 21 is rotatably mounted in the side members 40 of support 1 behind the insulator 3.

The shaft 21 could, of course, be rotated in any desired manner, as by a manually operated crank or a suitably controlled servomotor.

The dimensions of the lever transmission system are so selected that shaft 21 rotates through about 90.degree. as the switch contact 11 is moved from its off-position to its on position. By reference to FIG. 3 it will be noted that the maximum moment is exerted on lever 13 at the end of the switch-on movement, for a fixed shaft rotation force. Thus greater driving forces are available as tubular contact 32 engages the stationary electrical contact 26. The lever force transmission arrangement also serves to help lock the switch in the on position. In that case, as shown in FIG. 3, the drive shaft 21 and the pivot pins 24 and 25 are in a common plane, and rocker arm 22 and connecting arm 23 extend in a straight line so as to be in their dead center position.

The cam slot 16, previously described as being located in one of the walls of the insulating housing 9, has, as shown in FIG. 3, an upper curved portion 16a having a radius of curvature equal to the radial distance between bolt 14 and shaft 12. At the lower end of this curved portion the slot continues into a substantially straight portion 16b. When shaft 21 is first rotated in a counterclockwise direction from the off position as shown in FIG. 1, bolt 14 is in the bottom of the straight portion 16b of slot 16. Initially the bolt rotates housing 9 to an upright position as it moves in slot portion 16b.

After the housing 9 and the movable electrical contact 11 reach the upright position as shown in FIG. 2 further rotation of the shaft 21 moves the bolt along the curved slot portion 16a. This lifts the movable contact 11 within the housing 9. During this movement bolt 14 slides within the forked slide guide 17 and the quenching chamber portion 10 of contact 11 first moves about the stationary contact 26 so as to contain any arcing which occurs as the movable electrical contact portion 32 approaches the fixed contact 26. Finally, near the end of the rotary movement of shaft 21 the electrical contact portions 26 and 32 come into contact with each other.

During the switching off process the action occurs in a reverse sequence. First the electrical contact 32 is moved away from contact 26, then arcing occurs during the period when contact 26 is surrounded by the quenching chamber portion 10. The dimensions of the quenching chamber 10 are such that arc current is completely interrupted by the time the end of the chamber separates from the end of the upper contact 26. Thereafter the holder 9 and the contact 11 move back toward the support 1.

It will be readily apparent that the structure of the present invention permits the construction of switches occupying space substantially less than that required for the usual prior art switches. Moreover, it is possible to very easily maintain a voltage isolation for each switch from the front wall of the cabinets containing the switches or the control panels and also between the electrical contacts of the switch. A further advantage is the relatively small amount of mass that has to be moved as a result of the contacts being shortened to a fraction of their conventional lengths. The voltage conducting width of each connection terminal, or pole, is no greater than the width a of the connecting portions 4 and 6 as is shown in FIG. 4, the switch contacts themselves being well insulated.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.

Claims

We claim:

1. An electrical circuit interrupting device, comprising in combination:

a. a support frame;

b. a first insulator mounted on said support frame at one end thereof and projecting therefrom;

c. a first electrical contact mounted on said first insulator at a point spaced from said support frame;

d. a second insulator mounted on said support frame to project in the same direction as said first insulator but spaced therefrom;

e. a housing member pivotally mounted on said second insulator at a point spaced from said support frame;

f. a second electrical contact slidably mounted within said housing member, said second electrical contact being of tubular shape;

g. a quenching chamber on said second electrical contact, said quenching chamber being of tubular shape;

h. lever means pivotally connected to said support frame;

i. a bolt means mounted on said lever means;

j. connected means on said second electrical contact for engaging said bolt; and

k. cam means on said housing member, whereby said housing member is initially swingable from a position between said insulators to a second position where said first electrical contact and said second electrical contact are in alignment, and whereby further swingable movement of said lever means urges said electrical contacts to engagement.

2. The combination defined in claim 1, including roller means on said bolt means engaging said cam means.

3. The combination defined in claim 1 wherein said bolt means is located on said lever means at a fixed distance from the lever pivot, and wherein said cam means includes a cam member having a surface which has a radius of curvature equal to the radial distance of said bolt from said lever pivot.

4. The combination defined in claim 3 wherein said cam member further has a linear surface located at the end of said curved surface for effecting the pivotal movement of said housing member.

5. The combination defined in claim 1 wherein said connecting means has a fork shape formed of a pair of parallel members slidably engaging said bolt means on opposite sides thereof.

6. The combination defined in claim 1 wherein said quenching chamber means includes a tubular member connected at the end of said second electrical contact.

7. The combination defined in claim 1 wherein said member is of insulated material with said cam means being mounted on a wall of said housing member.

8. The combination defined in claim 1 wherein said lever means includes a pair of spaced substantially parallel links, and a trough-shaped connecting member formed of insulating material mounted between said links, and wherein said cam means moves said housing member into said trough-shaped member when said housing member is in a position between said first and second insulators to thereby insulate said second electrical contact from ground or from parts at a different electrical potential.

9. The combination defined in claim 1 wherein said lever means includes a shaft member rotatably mounted in said support frame.

10. The combination defined in claim 9 wherein said lever means includes a rocker arm fixed to said shaft member for rotation therewith, a rod member having a first joint pivotally connected to said rocker arm at a point radially spaced from the axis of said shaft member, and further connecting means connecting a second joint located on said rod at a point spaced from said first joint to said links whereby when said electrical contacts are in engagement the axis of said shaft member, and said first and second joints on the rod member are in a common plane.

11. The combination defined in claim 1 wherein said housing member has a length less than the distance between its pivotal mounting point on said second insulator and said support frame whereby said housing member and said second electrical contact can be moved by said lever means to a position between said first and second insulators and said support frame.

12. The combination defined in claim 1 including a flexible current lead electrically connecting said second electrical contact and an associated current carrying line.