US2574770A - Electric switch - Google Patents

Description

J. J. ZELLER ELECTRIC SWITCH Nov. 13, 1951 4 Sheets-Sheet 1 Filed June 29, 1949 Nov. 13, 1951 J. J. ZELLER 2,574,770

ELECTRIC SWITCH Filed June 29, 1949 4 Sheets-Sheet 2 M mum l||||||||l| Illlllllllll 4015i: .5. I g w [27 NH C i & 1 JUEEIJZEZ/ M 3 1: 3

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,[JZQ/ZEF 4 Sheet'sSheet 3 I III Jage J. J. ZELLER ELECTRIC SWITCH Nov. 13, 1951 Filed June 29, 1949 NOV. 13, 1951 J J ZELLER 2,574,770

ELECTRIC SWITCH Filed June 29, 1949 4 Sheets-Sheet 4 A HHHI FLO/7 T ACTl/A TED I 7 Patented Nov. 13, 1951 ELECTRIC SWITCH Josef J. Zeller, Wauwatosa, Wis., assignor to Square D Company, Milwaukee, Wis., a corporation of Wisconsin Application June 29, 1949, Serial No. 101,985

This invention relates to electric switches and refers particularly to pressure switches of the type used with air compressors and water pumps, but capable with slight modification of being float actuated to maintain a predetermined level of liquid in a tank.

One of the objects of this invention is to provide a switch .of the character described which will function equally well when used either as a float switch or as a pressure switch despite the fact that in the one case the actuating force is relatively slight while in the other it may be very substantial.

In this connection it is more specifically an object of this invention to provide'an electric switch which will snap open and shut with a positive action regardless of the service for which it is used.

A further object of this invention to provide an improved manner of incorporating a pressure differential spring in a switch of this type, and whereby adjustment of the differential spring in nowise affects the operation of the switch except to the extent that it either increases or decreases the diiierential between the opening and closing pressures.

Another object of this invention is to provide an improved manner of imparting opening and closing motion to the carrier of the movable switch contacts from the slow movement of the actuating mechanism.

In this connection it is another object of this invention to provide a switch of the character described in which the desired snap action is achieved through use of a bowed leaf spring reacting between two pivoted levers one of which is pivotally connected to the actuating member so that slow movement of the actuating member rocks the same to carry the end of the bowed spring attached thereto across dead center to thereby snap the contact carrier from one position to the other.

Another object of this invention is to provide a switch of the character described which when float actuated includes means to assure against diminishing or indecisive contact pressure as the float gradually rises and the switch tripping point is approached.

A still further object of this invention is to provide a switch of the character described which has a far more lively action than switches heretofore available for this service, and which by its design and construction is exceptionally flexible and may be readily applied to different types of service.

With the above and other objects in view, which will appear as the description proceeds, this inventidn resides in the novel construction, com- 7 Claims. (01. 200-83) 1 pressure source.

ment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a side view of a switch embodying this invention, said view showing the switch housing and diaphragm in section and illustrating the switch in its normally closed condition;

Figure 2 is a view similar to Figure 1 but showing only the essential parts of the switch mechanism, with the switch held open by pressure on the underside of the diaphragm;

Figure 3 is a horizontal sectional view through Figure l on the plane of line 3-3;

Figure 4 is a front view of the switch showing part'of the main spring broken away and illustrating particularly the manner in which the differential spring is incorporated in the assembly.

Figure 5 is a horizontal sectional view through Figure 4 on the plane of the line 5-5 Figure 6 is a view partially in side elevation and partially in longitudinal section illustrating the switch adapted for float actuation; and

Figure 7 is a sectional view taken through Figure 6 on the plane of the line l'l.

Referring now particularly to the accompanying drawings in which like numerals indicate like part throughout the several views, the numeral 5 designates a generally U-shaped main frame for the switch mounted in a housing 6.

If the switch is to be fluid pressure actuated as, for instance, in air. compressor or water pump service, a diaphragm l is secured acros a hole in the bottom wall 8 of the housing by being clamped between the housing bottom wall and a diaphragm head 9. The interior of this head provides a diaphragm chamber connectable with the If the switch is to be float actuated the diaphragm head is replaced by a pair of laterally spaced brackets I 0 between which a lever H is pivoted as at !2, a shown in Figures 6 and 7.

In either case motion is adapted to be imparted to a main lever l3 to actuate the switch mechanism and to open and close the switch which is indicated generally by the numeral l4.

As is customary the switch M has pairs of cooperating stationary and movable contacts l5 and 55 respectively, the former mounted upon an insulated terminal block l1 and the latter upon an insulated carrier IS with individual contact springs I3 for each pair thereof. The terminal block is suitably secured to the main frame 5 by screws which pass through a boss 2| on the underside of the terminal head and are threaded into ears 22' extending in from the upperfront portion of the main frame side Walls 23. This manner of mounting the terminal head facilitates the adaptation of the switch to either normally open or normally closed service.

The main frame 5 is a stamping and in addition to its side walls 23 which have their front edge portions cut out as at 24, it includes a bottom wall 25, the front and back portions of which are offset downwardly to provide feet upon which the switch mechanism rests. These flat supporting feet are seated upon the bottom wall of the housing 6 above the front andfback marginal portions of the diaphragm 1 and are secured in place by screws 25 which pass through the marginal edge portion of the diaphragm head 9, the diaphragm and the bottom wall 8 of the housing to be threaded into the feet.

At its foremost portion the frame 5 has an inclined upwardly directed lip 21 to which a U shaped bracket 2B i secured. The sides of this L l-shaped bracket have aligned notches 29 facing rearwardly. The forepart of theframe also has a lateral projection 31.! at one side thereof t which an upright stem 3| is secured in parallel spaced relation to a longer upright stem 32 also anchored to the forenar't of the frame medially between the two arms of the ll-shaped bracket 2-8. The longer stem 32 has a main spring 33 mounted thereon while the shorter stem mounts a differential spring 34. This diiierential spring is normally confined between a shoulder .35 on the stem 3| and an adjusting nut 35 threaded to the upper end of the stem.

The main spring 33 is confined between an adjusting nut :31 threaded on the upper portion of the stem 32 and a shelf 38 resting upon the free end of the main actuating lever 13 to thus at'all times ,yieldingly urge the lever downwardly.

For float actuation neither of the springs just mentioned is required. Hence, these-elements are omitted when the switch is to .be float actuated.

The main actuating lever -|3"is received-between the side walls 23 of the mainframe 5 and is pivotally connected thereto by a cross pin 39 at a point near the lower rear portion of the frame. The main actuating lever I3 is a U-shaped stamping with its flanges 40 lying closely adjacent to the inner surfaces of the frame side walls. Its web 4| has V-shaped indentations 12 against which pointed fingers 43 extending up from a diaphragm plate 43 bear to lift the main lever against the op osition of the spring 33 in response to pressure in the diaphragm chamber, the fingers 43 passing through holes- .4 in the main frame.

Each side wall 23 of the main frame has a hardened plate 45 accurately located thereon and riveted thereto. The front marginal edge .of each plate Q5 has a V-shaped notch 46 therein in line with the cutout :24 of the side walls of the frame proper. These .notches 45 ;are transversely aligned and receive knife edges 41 projecting rearw-ardly from the contact carrier l-B.

For all intents and purposes, the plates '45 constitute part of the main frame -5 and are separate pieces only to obviate the .need for hardening the entire frame to secure desired hardness for the :notches 4.5. Being fiat pieces the lates 45 may be hardened without danger of deformation, as is also the case of the separate U-shaped clip 28.

The contact carrier I8 is preferably made up of two sheet metal stampings 48 and 59 riveted together as at 50. The stamping 48 is essentially a fiat lever and has the knife edges 4'! formed directly thereof while the stamping 49 is generally a 'U-shaped structure and has an insulated contact carrying arm 5| secured thereto.

By virtue of the engagement of the knife edges .41 in the notches 46 the contact carrier is rockably supported for movement between switch open and switch closed positions, these limits of motion being defined by the collision of a laterallyprojeetin'g arm 52 on the lever 48 with either of two stop abutments 53 and 54 both of which are formed as part of the adjacent side wall of the main frame 5.

The arm 52 also provides means for opening a pressure relief valve 55 (shown in light lines in Figure 4) as the switch is opened. Such relief valves are customarily employed where the switches are used for the control of air compressors and have as their purpose to bleed pressure from the pressure chamber of the compressor as the compressor stops so that subsequent starting of the compressor will be easier.

Up and down movement of the main actuating lever |3 is imparted to the contact carrier H3 in a novel manner (now about to be described) which assures a more lively switch action and generally improves the operation of the switch. It will be noted that the notches 46 and the notches 29 are opposed to each other, that is, they face each other. The lever 48, which forms part of the contact carrier, is pivoted in the notches 4e and extends forwardly toward the other set of notches 29. Hence, it projects toward an intermediate lever 55 which is embraced by the arms or flanges of the main actuating lever l3 and is pivotally connected thereto as at 51, the pivot being a pin mounted in appropriate holes in the side flanges or arms of the lever I3 and passing through slightly elongated holes 58 in downstruck ears 59 on the intermediate lever 56, the major axis of the elongated holes 58 being parallel with the lever 55.

The lever 56 has knife edges 60 received in the notches 29 and the rear end of the lever opposite its "knife edges has a spring seat 5| formed thereon. This spring seat is parallel to and spaced a short distance from a similar spring seat 63 on the lever 48. A bowed leaf spring 63 has its ends hooked onto these spring seats 5| and 52 and yieldingly urges the same apart. Hence, the bowed spring 63 holds the knife edges 4! of the contact carrier in their notches l6 thereby retains the contact carrier in position and also holds the knife edges 60 of the intermediate lever 56 in their notches '23. Also, depending upon whether or not the pivot 51 is above or below the dead center plane joining the bottom of the notches 29 with the axis of the pivot 39, the bowed leaf spring 63 holds the contact carrier in its switch open or switch closed position respecti-vely.

Thus as shown in Figure l as long as the main lever 1| 3 is held down by the spring .33 and the pivot axis 51 is below the defined dead center plane'the spring seat 6| will be below the dead center plane joining the bottoms of the notches 29 and 46 and this disposition of the spring seat 5:! so directs the thrust .of the bowed spring that the contact carrier is yieldingly urged thereby to its switch closed position shown in Figure 1.

As the pressure within the diaphragm chamber overbalances the force of the spring 33 and the actuating lever l3 moves upward the pivot 57 crosses dead center and thereby swings the intermediate lever 56 on its knife edges 60 to the position shown in Figure 2 at which the spring seat 6| is above the dead center plane joining the bottoms of the grooves 29 and 46. With such reversal of the position of the spring seat Bl the thrust of the bowed spring 63 snaps the contact carrier to its switch open position shown in Figure 2. The described relative motion between the main lever l3 and the intermediate lever 56 is permitted by the elongated shape of the openings 58.

The differential spring 34 by which the differential between the pressures at which the switch is opened and closed may be adjusted, is so incorporated in the mechanism as to assure against the possibility of its presence and adjustment affecting the action of the switch in anywise. Hence, the shelf 38 upon which the main spring bears has an arm 65 projecting from one end thereof and apertured to loosely receive the stem 3!. When the main lever I3 is in its lowest position in which it is normally yieldingly held by the spring 33, the top of the arm 65, which preferably has two radial ridges 66 at diametrically opposite sides of the stem 3|, is spaced from the washer 61 interposed between the bottom of the differential spring 34 and the shoulder 35. Consequently, the main lever l3 may be lifted for a distance without opposition from the differential spring, and since the differential spring always bottoms on the shoulder 35 before the main lever descends far enough to trip the switch closed, closure of the switch takes place at a pressure determined solely by the setting of the main spring.

On the other hand, durin elevation of the main lever 13 to trip the switch open, the diiferential Spring 34 is lifted off the shoulder 35 and the load thereof added to that of the spring 33 before the lever l3 has risen high enough to trip the switch. The differential spring thus acts only during opening of the switch and thereby determines the differential between the pressures at which the switch opens and closes; the greater the tension on the spring 34, the higher the pressure needed to open the switch. Therefore, by increasing the tension on the spring 34, which is done by tightenin the adjusting nut 36, the

span or differential between the opening and closing pressures is increased and vice versa.

Attention is directed to the manner in which the shelf 38 is constructed and mounted upon the free end of the lever 3. It is conveniently made as a channel shaped stamping having upwardly pressed knobs 68 positioned to properly center the main spring and slots 69 in its. web to receive upstanding tongues 70 on the flanges of the actuating lever. Forwardly and rearwardly of the tongues the flanges of the actuating lever have bearin shoulders H upon which the shelf 38 rests.

The strength of the bowed spring 63 depends upon the service for which the switch is to be used. For air compressors where the opening of the switch is accompanied by the actuation of a pressure relief valve the bowed spring must have maximum strength. ;For water systems where the opening of the switch does not entail concomitant actuation of a pressure relief valve and between the levers.

where the pressures involved are generally less than that encountered in air compressor service, a medium strength spring is used. For float actuation a still lighter spring is employed.

When the switch is adapted for float actuation the diaphragm chamber, the main sprin 33 and the pressure differential spring 34 are omitted. Consequently, the only force holding the pivoted main actuating lever 13 down is that derived from the relatively light bowed spring 53. The spring 63' thus, of course, also provides the contact pressure to hold the contact carrier IS in its switch closing position.

As noted hereinbefore, in this embodiment of the invention a float lever H is pivotally mounted on the underside of the switch and this lever, which may be considered the actuator proper, has a motion transmitting connection with the pivoted lever 13 so that as the lever H moves up and down with the float it will impart similar movements to the lever 63. The pivot l2 for the lever ll may be either rearwardly or forwardly of its connection with the lever i 3, the former condition being illustrated in Figure 6. In this case ascent of the float lifts the lever l3 to effect opening of the switch and descent of the float lowers the lever 13 to effect closure of the switch.

If the pivot pin I2 is moved from its position shown in Figure 6 and instead passed through a second set of holes and 75 respectively in the brackets Hi and the head of the lever II, the reverse condition obtains, i. e., ascent of the float closes the switch and vice versa.

The motion transmitting connection between the levers II and i3 comprises two parallel transversely spaced links ll pivoted as at 18 to the lever l3 and to the lever II by means of a cross pin 19. The cross pin 19 passes through holes in the lower ends of the links T! and the flanges ll of the U-shaped head of the float lever l I.

The clearance between the pin 19 and the holes in which it seats is purposely large to provide a degree of lost motion in the connection As long as the lever II is in its lowermost position this lost motion is taken up by the weight of the lever. As the float lever ll rises the lost motion or play, of course, must be taken up in the other direction before motion is transmitted to the lever I3.

The limited freedom for independent motion between the levers I! and [3 resulting from this play in the connection therebetween enables a coil spring confined between the bottom of the lever 13 and the pin 19 to assure the desired decisiveness in switch action despite the relative weakness of the spring 63. A bridging piece 8| resting upon the flanges I I of the float lever and provided with a hole 82 holds the lower end of the coil spring in position bearing upon the cross pin 79, while the upper end of the spring is received in the depressed pocket in the bottom of the lever I 3.

The manner in which the spring 80 precludes indecisive contact pressure is as follows: Without the spring 80 and the play or lost motion which it can take up, as the lever I3 rises a point is reached where the contact pressure provided by the light leaf spring 63 balances the contact springs l9 and the contacts begin to ease off. However, with the coil spring 30 before this point of balance is reached the force stored in the spring 80 overcomes the spring 63' and by 75 virtue of the play or lost motion in the connecagar 7220 7 .tion :between the levers II :and 13 snaps "the switch open.

From the foregoing. description taken in connection with thezaccompanying drawings it will be readily apparent to those skilled in the art that this invention :provides "a switch which is .verywell adapted for either pressure .or float actuation and that it possesses many advantages over switches heretofore available for this purpose.

What I -claim as .my .invention is:

l. lInian electric snap switch adapted for pressure and. float actuation: a 'frarne providing opposed knife edge seats; a contact carrier having knife :iedges engaging one of said seats, .said :contact-carrier:carryingithe movable contacts of the switch :for movement to and from switch closing position by rocking motion about itsknife edges; an intermediate, lever havingknife edges engaging'the other of said knife edge seats, said con- :tact barrier and intermediate lever extending from :their respective knife edges towards each other and having adjacent but spaced .apart spring seats; a spring tensioned between said spring seats and ,-yieldingly urging said. spring seats apart and to opposite sides of a dead center plane connecting the opposed knife edge seats; and an actuating lever pivotally mounted upon the :frame and having pivotal connection withthe intermediate lever so that-rocking of the actuatinglever-about its pivotal connection with the frame-swings *the intermediate lever about its knife edges to open and close the switch.

2. In an electric switch of the character described: a frameincluding spaced side walls provided with notches inthe front edges thereof; a carrier for the movable contacts of the switch having knifevedges received insaid notches; an actuating lever flietween the side walls of the frame and pivoted thereto, the free'end of the actuating lever extending beyond the notched front edges of the side walls and beyond the contactor carrier pivoted therein; an intermediate lever :medially pivotally connected to the free end portion of the actuating lever; knife edges-on the end of the intermediate lever nearest :the free end of the actuating lever; means on the adjacentportion of the frame providing notches in which said last named knife edges are received; a spring seat on the inner end of the intermediate lever; a spring'seat on the contactor carrier facing the spring seat on the intermediate lever; and a spring tensioned between said seats and urging them apart to thus snap the contactor carrier from one position to the other as the actuating lever swings on its pivot to carry its connection with the intermediate lever across dead center, the pivotal connection between the intermediate lever and the actuating lever having sufficient 110st motion to enable said connection to swing across dead center as the actuating lever swings on its pivot.

3. In a snap switch of the character-described: a frame having two pairsof knife edge receiving notches. spaced apartand facing each other; a carrier for the movable contacts of the switch having knife edges pivotally received in one of said pairs of notches and adapted to carry the movable contacts of the switch from one position to the other as said carrier rocks upon its knife edges; means for defining the limits of said rock- ;movement; a main lever pivotally connected to the frame adjacent-to said pair of notches in which "the knife edges of the contact carrier are pivoted, the free end of said lever being adjacent to the "other pair .;of notches; an intermediate lever having knife edges pivotally engaged in said-other pair of notches and extendingztherefrom toward the first pairof notches; :meansv pivotally connecting said'intermediate lever medially ofits ends'tothefree end portion .ofthelmain lever; spring seats 'on the intermediate lever and the contact carrier spaced apart but facing each other; and a bowed spring confined between said spring seats to yieldin'gly'urge the same apart and thus hold thecontactparrier at one or the'other of its limits of movement dependinguponthe position of the main and-intermediaterlevers.

4. The switch of claim Bfurther characterized by the provision-of a compression spring acting upon the main lever-andproviding a force tending to rock the lever about its pivotalconnection with the-frame in one direction; and fluidpres- .sureiresponsive means acting upon the mainlever and providing a force tending to rock the lever in the opposite "direction.

5. In a switch of the character described: *a frame having spacedside walls, saidside walls having-knife-edge receiving notches opening :to the front of the frame; means on the forepart of the frame providing another set of knife edge receiving notches facing rearwardly toward the first designated set of notches; a carrier forthe movable contacts of the switch having'knife edges received in the first designated notches to mount the contactcarrier forrocking motion; means defining the limits of said rocking motion; a main lever betweenthe side walls of the frame'and-piv oted thereto on-an axis spaced rearwardly and downwardly from the first designated knife edge receiving notches with the free end of the lever adjacent to said other setof notches at the forepart of the frame, said lever having transversely spaced arms; an intermediate lever embraced by the arms of "the main lever and medially pivotally connected thereto near the free -endof the main lever; knife edges on the intermediate lever engagingin the set of notches at the forepart of the frame; a spring seat on the intermediate lever rearwardly of its pivotal connection with the main lever; a spring seat on the contact carrier facing the spring seat on'the intermediate lever; and a bowed'leaf spring having its free ends bearing against the spring seats to yieldingly urge the same apart and thereby :hold the knife edges of the contact-carrier in their respeotive notches and yieldingly hold the contact carrier in one or the other of its llil'llts'df rocking motion depending upon the position of the main and intermediate levers.

6. In a-switch of the character described: a movable contact having a contact spring which is tensioned as the switch is closed; a pivoted actuating lever; mechanism connected between the movable contact and the actuating lever for snapping the movable contact from one position to the other as the actuating lever rocks on its pivot, said mechanism including a 'bowed spring which holds the movable contact in its closed position and thereby tensions the contact spring; an actuator; a motion transmitting connection between the actuator and said pivoted actuating lever, said motion transmitting connection having a degree of lost motion; and a spring reacting between the actuator and the pivoted actuating lever and yieldingly urging said members apart so that during movement of the actuator toward the pivoted'actuatmg'lever the lost motion in the connection is taken up before movement is imparted to-the pivoted actuating lever, -and'fcrc'e is stored in said spring to snap the switch open before the instant is reached at which the forces of the contact spring and the bowed spring would balance.

7. In a switch of the character described: a frame; a main lever pivoted at one end portion to the frame, said main lever having spaced apart opposing flanges thereon extending to its other end portion and disposed to swing edgewise with the main lever; an intermediate lever received between the flanges on said other end portion of the main lever; a pivotal connection between one end of said intermediate lever and the frame adjacent to said other end portion of the main lever; a motion transmitting connection between the main and intermediate levers whereby pivotal motion of the main lever is translated into rocking motion of the intermediate lever about its pivotal connection with the frame; switch means connected with the opposite end of said intermediate lever to be actuated thereby between switch-open and switch-closed positions; a bridge-like saddle overlying the intermediate lever and said other end portion of the main lever, said saddle seating upon edge portions of the main lever flanges; an interlocking connection between each of said flanges and the saddle hold- 10 ing the latter against movement relative to the main lever except in a direction to lift the saddle ofi of said edges of the main lever flanges; and a spring acting upon said saddle to hold the same against movement relative to the main lever in said direction to thus maintain the saddle operatively connected with the main lever, said spring acting through the saddle to apply a force on the main lever yieldingly urging the same and the intermediate lever connected therewith toward a position at which said switch means actuated by the intermediate lever is at one of said switch positions.

J OSEF J. ZELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,610,213 De Ville Dec. 7, 1926 2,083,343 Naul June 8, 1937 2,157,156 Abendroth May 9, 1939 2,255,115 Helle Sept. 9, 1941 2,453,861 Rothwell Nov. 16, 1948

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