US2654816A - Electric switch - Google Patents

Description

Oct. 6, 1953 3 Sheets-Sheet 1 Filed Oct. 51 1951 J. J. LAWSER ELECTRIC SWITCH Oct. 6, 1953 3 Sheets-Sheet 2 Filed Oct. 51, 1951 0,000 CSTKS 30,000 cs-ms. J

*AI R C mwm WAS 08 $303 .55

TOTAL CLEARANCE IN THOUSANDTHS OF Oct. 6, 1953 J. J. LAWSER 2,654,815

ELECTRIC SWITCH Filed Oct. 51, 1951 s Sheets-Sheqc s \\\\\\\\\\\\\\\\\NWII Jam J" Lam/$87 Patented Oct. 6, 1953 ELECTRIC SWITCH John J. Lawser, Philadelphia, Pa., assignor to Proctor Electric Com pany, Philadelphia, Pa.,

a corporation of Pennsylvania Application October 31, 1951, Serial No. 254,037

11 Claims. 7 l

The present invention relates to electrical switches of the type used in switching a load, such as a heating unit, from one electric supply line voltage to another.

The present invention is particularly applicable to wattage controllers of the type known as flashers, such as discussed in prior patents, for example U. S. Patent No. 2,357,225 issued August 29, 1944 to S. J. Roesch et al., and in the copend-ing applications of W. H. Vogelsberg, Serial No. 157,933, filed April 25, 1950, and Serial No. 250,326, filed October 8, 1951. In these devices heating unit coils are initially overenergized and after a predetermined interval are reduced in energization. This causes rapid initial heating of the heating unit to some selected temperature and subsequent energization at a lower wattage to maintain the selected temperature. In one particular flasher switch, the connections for overenergization are maintained through a latch member. On release of the latch the blades move to a new position permitting a change in electric connections to thereby establish the lower wattage to the heating unit. Under certain circumstances it has been found that the movement of switch members from the overenergization position to the normal energization position may cause an. arc-over phenomenon which has been termed pop-over. This is due to the establishment of a sustained electrical are between the first stationary contact position which is established at one potential and a second stationary contact position which is established at a different potential or is caused to operate at a different potential by the moving switch members. This situation is aggravated by high or overload currents that may be carried by the contacts, by bouncing of the contacts, by the absence of means to remove the are products, etc.

It is a prime object of this invention to eliminate pop-over from wattage controllers.

It has been found that adding mass to the blades to obviate this pop-over condition causes only a small percentage of improvement. .r

Under severe over-current conditions, increasing the mass of the moving blades does not give a sufiiciently satisfactory solution. Moreover, increasing the mass presents problems of space limitations and aggravates the contact bounce problem.

Another object of this invention is to provide means in a wattage controller for obviating the pop-over problem without materially increasing the mass of the moving blade.

The present invention is illustrated in the accompanying drawings as applied to a device of the general type disclosed in the copending applications of W. H. Vogelsberg. The pertinent portion of the switch structure and simplified schematic diagrams of the circuit necessary for an understanding of the present invention are shown in the drawings and set forth in the description that follows.

In the drawings,

Fig. 1 is an isometric view of the wattage controller to which the present invention is adapted;

Fig. 2 is a simplified schematic circuit diagram of the controller in its overenergization position;

Fig. 3 is similar to Fig. 2 with the parts in the normal energization position;

Fig. 4 is a section through the controller of Fig. 1 taken along line 4-4;

Fig. 5 is a partial front elevational view of the switch with the cover removed;

Fig. 6 is a partial rear elevational view of the switch;

Figs. 7 and 8 are sectional views taken along lines l-l and 8-8 of Fig. 5;

Fig. 9 is an exploded isometric view of the elements of a latch construction of the present invention;

Fig. 10 is a sectional l0l0 of Fig. 4;

Fig. 11 is a sectional view of a modified form of the latch construction, the view being taken along a plane indicated at H-l| in Fig. 4;

Fig. 12 is a fragmentary sectional view of the same taken similarly to Fig. 10;

Fig. 13 is a perspective of one of the walls associated with the latch member;

Fig. 14 is a perspective view of the latch member; and

Fig. 15 is an explanatory graph.

The wattage controller designated as I0 in Fig. 1 is of the type described in the aforementioned Vogelsberg applications. It comprises a switch case I l and cover plate l2 by which it may be secured to the panel of an electric range. A manual control knob I3 is used to select the particular desired operating temperature of the heating unit to be controlled. Resistance coils R1 and R2 in Figs. 2 and 3 represent such a heating unit. In these figures some of the nonpertinent details are omitted for circuit simplification, but it will be understood that resistances R1 and R2 are subjected to overenergization during an initial heating period by the controller [0 from a supply line l5, and after rapid attainment of a predetermined temperaview taken along line Preferably the latch member 22 has waflled end surfaces, as may be seen in Fig. 9. The pores of the latch member retain the grease, and the pockets formed by the waiiling of the end surfaces are considered to be a desirable refinement from the standpoint of enhancing the grease retaining action.

Another form of damping latch arrangement is shown in Figs. 11 to 14. In this embodiment, no resilient body is used. Rather, the clearance between the lands of the sidewalls a2 is reduced and a space on each side of the latch is filled with a damping grease given the general designation 5t. To help maintain the grease in the clearance space on each side of the latch and to improve the flow of the damping fluid, grooves El are formed in the sidewalls 42, as shown in Figs. 11 and 13. Further, a small hole 52 is provided in the body of the latch to permit equalization of the grease flow between the two clearance spaces. The edge portions of the latch 22a and the cooperating portions of the lands of sidewalls 42 are recessed at 5t and 55, respectively. I'he spaces provided permit improved storage capacity for the damping grease. The recesses of the latch member also provide scraper edges thereon.

An understanding of the effect of the clearances on, for example, the second embodiment, can be had by reference to Fig. 15. In this figure is plotted the length of time for the latch to move from one stationary contact position to the second stationary contact position as a function of the total clearances between lands and the body of the latchZZa. In the test from which this data was derived the driving force inherent in the bias of blades I6 and It was in the order of 180 grams. It can be seen from curve A that very little damping is obtained by the use of air as a fluid medium. As shown by B and C, substantial dam ing is obtained even at clearances in excess of .010 with use of fiuids or" 30,000 and 60,000 cstks. viscosity, respectively. Although much greater damping can be had by reducing clearances as shown in the vicinity of the .002" to .006" clearances, it is more advisable to use the damping characteristics which are substantially independent of change of clearance distances. For this reason these damping arrangements are substantially unaffected by wear as under severe service conditions. Larger clearances also help prevent gumming of the latch due to dirt accumulation. In the tests from which the curves B and C were derived, the greases used were of the type known commercially as DC (Dow Corning) 200, or equivalent. These greases are fairly heavy, and by their use in combination with either embodiment of the present invention, special glands or packings are unnecessary for grease retention.

The time for travel of a latch is given in Fig. '15 in half cycles of a 60 cycle/sec. alternating current. While it is normally considered that the arc should be extinguished at the first current zero, it was found that a great number of pop-overs occurred if the travel time was less than approximately 6 to 8 half cycles.

While the present invention is particularly intended for use in the manner described, it is intended that the invention shall be applicable to any use to which it may be applied by those skilled in the art. Further, while only two forms are considered within the scope of this invention.

I claim:

1. In a switching device for controlling an electrical heating load from an electrical supply line, a first stationary contact adapted to be connected to a line conductor at a first potential, a second stationary contact spaced from said first contact by a predetermined distance and adapted to be connected to a line conductor at a second potential, a movable contact arranged for movement between said stationary contacts and adapted to be connected to said heating load to apply said potentials thereto, said movable contact being spring-biased toward said second stationary contact, means including a movable member operatively associated with said movable contact for initially positioning and latching the movable contact in engagement with said first stationary contact, and for releasing said movable contact to permit it to move to said second stationary contact under its spring bias, and means for retarding movement of said member, to thus retard movement of said movable contact, suificiently to permit dissipation of any are drawn by said movable contact in moving from said first stationary contact and thereby prevent establishment of a continuous are between said stationary contacts.

2. In a switching device for controlling an electrical heating load from an electrical supply line, a first stationary contact adapted to be connected to a line conductor at a first potential, a second stationary contact spaced from said first contact by a pre etermined distance and adapted to be connected to a line conductor at a second potential, a movable contact arranged for movement between said stationary contacts and adapted to be connected to said heating load to apply said potentials thereto, said movable contact being spring-biased toward said second stationary contact, means including a movable member operatively associated with said movable contact for initially positioning and latching the movable contact in engagement with said first stationary contact, and for releasing said movable contact to permit it to move to said second stationary contact under its spring bias, means forming at least one stationary surface in close proximity to said member, and means including a fluid meduim between said member and said surface for retarding movement of said member, to thus retard movement of said movable contact, sufficiently to permit dissipation of any are drawn by said movable contact in moving from said first stationary contact and thereby prevent establishment of a continuous are between said stationary contacts.

3. In a switching device for controlling an electrical heating load from an electrical supply line, a first stationary contact adapted to be connected to a line conductor at a first potential, a second stationary contact spaced from said first contact by a predetermined distance and adapted to be connected to a line conductor at a second potential, a movable contact arranged for inovement between said stationary contacts and adapted to be connected to said heating load to apply said potentials thereto, said movable contact being spring-biased toward said second stationary contact, means including a movable member operatively associated with said movable contact for initially positioning and latching the movable contact in engagement with said first stationary contact, and for releasing said movable cont ct to permit it to move to said second stationary asses-1c contact under its spring. biasameansforming'at least one stationary surface in close proximity to saidmember so as to. provide a space between saidsurface andsaid member; and means-includ ing a fluid medium between saidmember and said. surface for retarding movement. of; said member, to thus retard movement of. said movable. con tact, suiiiciently'to permit dissipationzof any arc. drawn by said movable contact in moving from said first stationary contact and thereby. prevent establishment of a continuousarc'betweensaid stationary contacts, said space being characterized by the absenceof packingor the equivalent to maintain the fluid medium in said space.

4.. In a switching. device for controlling an. elec'- trical heating load froman electricalsupply line, a firststationary-c'ontact adapted'to be connected to a. line conductor at a. firstpotentiaLa second stationary contact'spaced fromsaid-flrst contact by a predetermined distance. and adaptedto be connected to a line. conductor at asecond potential,.a movable contact arranged for movement between said stationary contacts and adapted to be connected to said: heating load to apply said potentials thereto, said movable contact. being spring-biased toward said secondstationary contact, meansincluding. a. movable. member operatively asssociated with said movable contact for initially positioning and. latching the movable contactin engagement with said firststationary contact, and for releasing said movable contact to permit it to move to said second stationary contact under itsspring bias, said member having flat opposed faces, means forming stationary fiat surfacesin close proximity to-the opposed faces of said member,.andmeans including a fluid. medium between each of said surfaces and the adjacentface of said: member for. retarding movement of said member,. to thus retard movement of said movable contact. sufficiently to permit dissipation of any are drawn by. said. movable contact in moving from said first stationary contact and thereby prevent establishmentof. acontinuous arc between saidzstationary'contacts.

5. In aswitching device for controllingan-electrical heating load from. anelectricalsupply line, a first stationary contact adaptedtorbe connected to a lineconductor at afirst potential, a second stationary contact spacedfrom said firsticontact by a predetermined distance. and: adapted to. be connected to a line conductor at a: second potential, a movable contact arranged. for'movement between saidstationary contactssand adaptedto be connected-to saidheating load to-apply said potentials thereto,. said movable. contact being spring-biased toward said second stationary. contact, means including a movable member operatively associated with said-movable contact for initially positioning and latching the movable contact in engagement with said first stationary contact, and for releasing said movable contact to permit it to move to said second stationary contact under itsspring bias, said member having flat opposed faces and having an aperture. extending between said faces, means forming stationary flat surfaces in closeproximity to the opposed faces of said member, a resilientabsorbent pad carried within said apertureand engaging said surfaces, and afiuid-medium impregnating said pad, whereby movement of. saidmember is retarded, to thus. retard movement of :said'movable contact, sufficiently to: permit dissipationof any are drawn-.bysaid movablecontact'inmoving from said first stationary contact and" thereby prevent establishment of a continuous are between said stationary. contacts.

6. A device; accordingto claimfi, wherein said resilient pad. is compressed betweensaid stationary. surfaces;

to a line conductor at a first. potential, a second.

stationary contact spaced from said first contact by a predetermined distance. and adapted to be connectedto a-line-conductor at a. secondpoten tial, a movable contact arranged for movement between saidstationary contacts and adapted to be connected to saidheating load to apply said potentials thereto, said movable contact being spring-biasedtoward saidsecondi stationary contact, means including amovable member operatively associated with said movable contact for initially positioning and latching themovable contact in engagement-with saidfirst stationary contact, and for releasing said movable contact to-permit it to move. tosaidsecond stationary contact under its-spring bias; said member having flat opposed faces and having an aperture extending between said faces, said member also having scraper edges thereon, means forming stationary flat surfaceswith grooves'therein in close proximity-to the opposedfaces-of saidmember, and a fluidmediumwithin'said aperture and between said surfaces and thefac'esof said member for retarding movement of said member; to thus retard movement of said movable contact, suificiently'topermit dissipation of any are drawn by saidmovable-contactin moving from-said first stationary contact and thereby prevent establishment of a continuous are between said stationary contacts;

8*. In a switchingdevice for controlling-an electrical heating load from an'electrical-supply line, a first stationary contact adaptedtobe'connected to a line conductor at a first potential, a second stationary contact spaced from said first contact by-a predetermined distance" and adapted to be connected to a line conductor at a second potential, a movable contact arranged for'movement between said stationary contacts. and adapted to be connected to" said heating load to" apply. said potentials thereto, a movable member operatively associated with said movable contact for movement conjointly'therewith; said member having flat opposed faces" and having an aperture extendingbetween said faces, means formin stationary fiatsurfacesin close proximity to the op posed faces of said member,a resilient absorbent pad carried Within saidaperture and'engaging said'surfaces, and'a fiuid'medium impregnating said" pad, whereby movement of said member is retarded, to thus retard movement of said movable-contact, sufiiciently to permit dissipation of any'arc' drawn by said'movable contact in moving from said first stationary contact andthereby prevent establishment. of a continuous arc between said stationary contacts.

9. In a switching device for controlling an electrical heating loadfrom-an'electrical supply line,

a first stationary contact adapted to be connected to a line conductor'at a first potential, a second stationary contact spaced'from said first contact bya predetermined distance and adapted'to be connected toa line conductor at a secondpotential, a movablacontact' arranged for movement between .said :stationarycontacts and adapted to beconnected' to said heating load to apply said potentials thereto, a movable member operatively associated with said movable contact for movement conjointly therewith, said member having flat opposed faces and having an aperture extending between said faces, said member also having scraper edges thereon, means forming stationary fiat surfaces with grooves therein in close proximity to the opposed faces of said member, and a fluid medium within said aperture and between said surfaces and the faces of said member for retarding movement of said member, to thus retard movement of said movable contact, sufflciently to permit dissiptation of any are drawn by said movable contact in moving from said first stationary contact and thereby prevent establishment of a continuous arc between said stationary contacts.

10. In a system for flashing an electrical heating unit and for eifecting subsequent normal energization of said unit, a supply line providing different potentials, switch means operable between a flash position and a normal position and being biased toward the normal position, connections controlled by said switch means to effect flash and normal operation of said heating unit, means including a movable member operatively associated with said switch means for initially positioning and latchin the switch means in the flash position, and for releasing the switch means to permit the latter to move to the normal position, the switch means being subjected to different line potentials conducive to arcing in the process of switch-over from flash to normal operation, and means for retarding movement of said member to thus retard the switch-over action of said switch means, sufliciently to permit dissipation of any are and to prevent establishment of a continuous are through the switch means.

11. In a system for flashing an electrical heating unit and for effecting subsequent normal energization of said unit, a supply line providing different potentials, switch means operable from a flash position to a normal position, connections controlled by said switch means to effect flash and normal operation of said heating unit, the switch means being subjected to different line potentials conducive to arcing in the process of switch-over from flash to normal operation, a movable member operatively associated with said switch means for movement conjointly therewith, said member having flat opposed faces and having an aperture extending between said faces, means forming stationary flat surfaces in close proximity to the opposed faces of said member, a resilient absorbent pad carried within said aperture and engaging said surfaces, and a fluid medium impregnating said pad, whereby movement of said member is retarded, to thus retard the switch-over action of said switch means, sufficiently to permit dissipation of any arc and to prevent establishment of a continuous are through the switch means.

JOHN J. LAWSER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,040,405 Persons May 12, 1936 2,210,947 Myers Aug. 13, 1940 2,213,993 Myers Sept. 10, 1940 2,236,411 Metcalf Mar. 25, 1941

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