US2784275A - Current interrupting switch - Google Patents

Description

Filed June l, 1955 March 5, 1957 .L A. SENN CURRENT INTERRUPTING SWITCH 2 Sheets-Sheet l INVENTOR M hm BY @mf/,M

ATTORNEY March 5, 1957 Filed June l, 1953- J. A. sENN 2,784,275 CURRENT INTERRUPTING swITcH 2 Sheets-Sheet 2 INVENTOR Maxl@ A@.aq/mfaf ATTORNEY nited States Patent O CURRENT INTERRUPTING SWU` CH Jurg A. Senn, Milwaukee, Wis., assignor to Paragon Electric Company, Two Rivers, Wis., a corporation of Wiscousin Application June 1, 1953, Serial No. 358,689 4 Claims. (Cl. 200-91) This invention relates to alternating current interruptors and it more specifically resides in a switch for breaking an alternating current circuit at a point in the cycle when the current is at or near zero value, which switch has a movable contact member that may travel toward and away from a stationary contact and is cooperatively joined with one element of an electromagnet, the other element of the magnet being disposed to retain the movable contact member in Contact closed position when the magnet is energized and the contact member has been initially moved to the contact closed position, and which switch includes an operating member that is cooperatively joined with the movable contact member through resilient means and which may be moved to a contact opening position to exert a bias to urge the contact member to move away from contact closed position to open position, the movement to open position occurring upon the current in the magnet decreasing to or near zero Value.

The useful life of a switch is often dependent upon that of its contacts and since electrical corrosion of contacts due to interruption of substantial currents is a primary factor in determining Contact life it is desirable to reduce such corrosion to a minimum. In many application steps are taken to cause a quick extinguishment of the arc that occurs upon contact separation, Where size of the switch permits apparatus is often included to draw out and extend the arc path, or the contacts are disposed in a hood that aids extinguishment of the arc. In alternating current switches such means are directed toward the interruption of substantial load currents for any random point in the current cycle.

In a switch embodying this invention current interruption in an alternating current circuit occurs when the current decreases to or is in the proximity of zero value. Undesirable arcing is eliminated, thus reducing corrosion of the contacts and the invention may be employed in small manual switches as well as in larger sizes. Where in small manually operable switches, contact throw is dependent upon toggle action contact pre-ssures usually diminish as the operating elements are moved to the point of contact throw. It is common, in such switches, to use oversize springs to retain sufcient contact pressures. ln the use of this invention such oversize springs may be eliminated and suiiicient contact pressures are retained up to the point of contact throw.

It is an object of this invention to provide a switch for interrupting alternating current that minimizes the electrical corrosion that may occur at the contact surfaces.

It is another object of this invention to provide a switch that will retain suicient contact pressure up to the point of throw to avoid corroding of the contacts.

It is another object of this invention to provide a switch that will interrupt alternating current only when the current passes through that portion of the cycle at or near the zero value.

It is still another object of this invention to provide a switch for alternating current with contact opening means responsive to the cyclic current variations that may be adjusted to have contact separation occur at a selected moment with respect to the alternating current cycle.

These and other objects and advantages of this invention will appear in the description to follow. In the description reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration and not of limitation one specific form in which this invention may be embodied.

In the drawings:

Fig. 1 is a top plan view of an alternating current switch in which this invention is embodied,

Fig. 2 is a side View in elevation and in section of the switch viewed through the plane 2-2 in Fig. 1 with the manual actuator in Contact closed position,

Fig. 3 is a side View in elevation of the switch with the actuator thrown to contact opening position,

Fig. 4 is a side View in elevation of the switch with the parts thereof in the position assumed at the moment of Contact separation,

Fig. 5 is a side view in elevation of the switch with the contacts in open position,

Fig. 6 is a cross section view in elevation of the switch viewed through the plane 6 6 in Fi 7 and Fig. 7 is a graphical representation of an alternating4 current as is interrupted by the switch.

Referring now to the drawings, there is shown a rectangular mounting base 1 ot an insulating material such as phenol-aldehyde resin. Mounted near the left hand end of the base l, as viewed in Figs. l-5, is an upwardly extending mounting block 2 upon which is fastened a horizontal plate 3. The plate 3 is provided with a pair of upstanding spaced brackets 4 and threadedly receives a bias adjustment screw i that may be turned to adjust the vertical position of its upper end.

A pivot pin 6 passing through the brackets 4 of the plate 3 also passes through a pair of side tlanges 7 at one end of a movable contact lever 8. The anges 7 extend along a major portion of the lever 8 to impart desirable stiifness and disposed within the channel of the lever S is an actuating leaf spring 9. The spring 9 is attached to the pivoted end of the lever 8 by an assembly bolt 10 and extends to the left above the plate 3 to provide a contact closing spring portion 11 that rests upon the upper tip of the bias adjustment screw 5. The actuating spring 9 also extends to the right of the assembly bolt 1t) to provide a leaf spring portion 12 that may be dellected for biasing the Contact lever 3 to a contact open position, as hereinafter described.

On the shaft ot the assembly bolt 10 and beneath the lever 8 is a pair of spacers 13. Abutting the underside of the spacers 13 is a resilient contact arm 14 that extends beneath the lever 8 to form a leaf spring. The contact arm 14 is given an inclination for a normal position disposing its free end that mounts a movable contact 15, well beneath the lever 8. A terminal lug 16 is also received by the bolt 10 and a terminal nut 17 is brought up tightly on the lower end of the bolt 1) to hold the assembly in position.

A contact pickup screw 18 is threadedly received at the free end of the movable contact lever 8. The screw 18 has a head 19 disposed beneath the lever 8 to engage the tip of the contact arm 14 as the lever S moves upwardly. The position of the head 19 may be adjusted by turning the pickup screw 18 in the lever 8.

Centrally disposed on the upper face of the base 1 and riveted in position is a conductor plate 20 that threadedly receives a stationary contact stud 21. The stud 21 mounts a stationary contact 22 in facing relation with the movable contact 15 to be engaged` and disengaged thereby upon movement of the contact arm 14. Also mounted on the conductor plate 2i`is a eld piece 23 of an electro-magnetV 2d. The eld piece 23 isi in the form of a yoke with two upwardly disposedpole faces and wound about the field piece 23 is awinding 25 comprising seven' turns of alow resistance ribbon conductor. Oneend of the winding 25 is pressed between the upper face of the conductor plate 2t) and the bottom face of the eld piece 23. The other end of the winding- 25 is secured to a binding post 26 in the base 1. A terminal lug 27 is received by the binding post 26 and a terminal nut 28 is brought tightly down upon the-lug 27. Completing the electromagnet 24 is a yokey shaped armature 29 secured. to the movable contact lever 8 that is disposed above the field piece 23 to be attracted downwardly thereby upon energization ofthe Winding 25.

At the right hand end of the base 1 is a vertically eX- tending post 3@ and pivotally mounted to the post 3l) with a common pivot 42 are a pair of toggle arms 31 and 32. Each toggle arm 31 and 32 has a pair of movement limiting ears 33 which are disposed to strike a pair of pins 3a extending outwardly from the post 30 to arrest the pivotal travel of the arms 31, 32. A toggle spring 35 is connected at its ends to the toggle arms 31, 32 to move the toggle arms 31, 32 downwardly, as shown in Fig. 2, when the spring 35 is disposed beneath the pivot 42 of the arms 31, 32 and to move the arms 31, 32 upwardly, as shown in Fig. 3, when the spring is passed above the pivot 42. To actuate the toggle there is provided a notched toggle operator 36 that engages the free end of the toggle arm 32. Movement of the operator 36 upwardly or downwardly will move the toggle arm 32 in like direction to carry the toggle spring 35 above or below the pivot d2 of the arms 31, 32. As the spring 35 moves across the pivot center the toggle arm 31 will be moved accordingly with a snap action.

The bias adjustment screw 5 is set to deflect the free end of the portion 11 of the actuating spring 9 slightly upwardly to apply a bias force to the contact lever S. This bias acts to deect the lever 8 downwardly to the position as shown in Fig. 2, when the toggle arm 31 is in lower position. The resilient contact arm 14 will then engage the movable contact 15 with the stationary contact 22 and the lever 8 is broughtA down on the top of the movable contact 15 to increase contact pressure beyond that otherwise applied by the leaf spring 14. With the terminal lugs 16 and 27 connected in an alternating current circuit to be controlled the energization of the electro-magnet 24 will urgethe armature 29 downwardly, thus providing a force opposing an upward movement of the Contact lever S.

To open the switch contacts the toggle operator 36 is moved upwardly to carry the toggle arm 32 into its upper position. As the toggle spring 35 passes above the pivot 42 of the toggle arms 31, 32 into the dotted position shown in Fig. 2 the toggle arm 31 is in turn moved upwardly to the position in Fig. 3. Arm 31 then deflects portion 12 of the actuating spring 9 upwardly to urge the contact lever toan open Contact position in opposition to the bias of the spring portion 11. The position or' the switch elements at this point of operation is shown in Fig. 3. winding 25 of the electro-magnet 2dthe combined bias of the spring portion 11 and the downward attraction'of the magnet 2dretains the lever 8 in down, or contact closed position, regardless of the bias of thespring portion 12. As the alternating current in the winding'25 decreases the combined bias of spring 11 and attraction of magnet 2d acting on lever Stalls in value and becomes less than the bias of the spring portion 12 urging the lever upwardly. The contact lever 8 will then move upwardiy, however, movable contact 15 will remain Vin` closedposition since contact arm 14 is normally inclined to vassume a position well below the lever 3.V The lever With a substantial current ow in they 8 when moving upwardly, carries the head 19 ofthe pick-- up screw 18 into engagementwith the tip of the contact arm 14, as shown in Fig. 4. The movable contact 15 is now disengaged from the stationary contact 22 as the lever 8 continues to move toward its fully open position shown in Fig. 5.

To reclose the switch the toggle operator 36 may be moved downwardly to carry the free end of toggle arm 32 downwardly and snap the toggle arm 31 to its lower position. Spring portion 12 will no longer be deected and the portion 11 of spring 9 will move the contact` lever 8 downwardly. The position shown in Fig. 2 is again assumed.

By adjustment of the contact pickup screw 13 the instant of contact sparation can be regulated to occur when the current is at or near zero value. Referring now to Fig. 7, there is depicted therein a sinusoidal current 37 with a horizontal axis 38 that indicates zero current value. The ordinate 39 corresponds to that point in time when the spring portion 12 is deected'upward by the toggle to bias lever 8 toward open or raised position. This point may occur at any point in the cycle of current lluctuation and has been arbitrarily selected in Fig. 7 for a current value that will cause the magnet 24 to retain the switch closed. As the current passes from its peak value downwardly the magnetic attraction of magnet 24 will-correspondingly decrease until the upward bias of spring portion 12 will move lever 8 upwardly. The ordinate d@ represents the point of initial upward movement of lever S. Contact separation will now be determined by the position of the head 19 of pickup screw 1S and the acceleration of the lever 3. By

adjustment of the screw 13 the instant of pickup of' contact 15 may be predetermined to occur as the current diminishes or nears its zero value, as at the ordinate 41.

There is thus provided through the employment of this invention a switch that will interrupt alternating current at a point in the cycle when the current flow is small. Electrical corrosion of the cotnacts such as pitting andburning will be minimized and contact life prolonged. Contact pressure does not diminish to insuicient value and oversize springs are not required. The contact arm 14-which is in the form of a leaf spring retains pressure between the contacts as the lever 3 moves upwardly, and contact separation is caused by the impact of the head 19 against the arm 14 rather than by passing a toggle across its center.

I claim:

l. In a switch the combination comprising a stationary contact, a movable contact lever movable between contact opening and closing positions, contact lever operating -means cooperatively engaged with said contact lever movable to two positions to alternatively apply contact opening and contact closing bias to said lever to urge said lever toward its contact opening and contact closing positions respectively, a movable contact cooperatively engaged through resilient means with said lever disposed in facing relation to said stationary contact engageable with the stationary contact upon throw of said lever toward contact closing position and retained in contact closed engagement by said resilient means upon initial throw of said lever from contact closing position, a contact pickup member movable with. saidlever disposed to engage said movable contact when said lever reaches a selected position in its throw toward contact opening position and to carry said movable contact to open position, and an electro-magnet positioned adgla ent` toV said lever and disposed to attractively retain said lever when energized by substantial current in contact'closing position when said lever has been moved to such position in response to said. operating means, said magnet permitting said lever to move toward contact opening position in response to an opening bias lof said operating' 2. A switch in accordance with claim 1 wherein said contact lever operating means comprises a leaf spring secured at a midpoint to said lever with one end deected to impart a bias to said lever urging said lever toward contact closing position and with the other end deectable to impart a contact opening bias to'said lever greater than the contact closing bias.

3. A switch in accordance with claim 1 wherein the electro-magnet has a winding in series relation with said contacts.

4. A switch in laccordance with claim 1 wherein the contact pickup member is adjustable in position with respect to said lever to select the position of said lever at which contact pickup is made for breaking the circuit of said contacts when the current therein is passing through a particular position of its periodic cycle.

References Cited in the file of this patent UNITED STATES PATENTS Nicholson Nov. 9, 1880 Hallock June 13, 1916 Wise July 11, 1933 Noyes Feb. 12, 1952 Casey Nov. 17, 1953 FOREIGN PATENTS Austria Jan. 25, 1952 Great Britain Iune 15, 1936 Great Britain Nov. 30, 1938 Great Britain Dec. 7, 1944 Germany Sept. 11, 1937

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