US2692922A - Resetting device for switches - Google Patents

Description

J. C. MILLSAP RESETTING DEVICE FOR SWITCHES Filed July 13, 1953 Oct. 26, 1954 HTTURNEYE Patented Oct. 26, 1954 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to switches and more particularly to a resetting device for a switch of the type adapted to automatically open a circuit when a particular condition exists.

Although not necessarily restricted thereto, the present invention will be described in connection with a safety switch of the type disclosed in my copending United States patent application Serial No. 278,333, filed March 25, 1952, now abandoned. In the copending application, a switch is disclosed which includes a fluid pressure operated diaphragm. The arrangement of the switch is such that when the fluid pressure in the line to which the switch is connected falls below a predetermined pressure, certain contacts open to break a motor circuit thereby stopping the pump to which the motor is connected.

The application above referred to also discloses manually resettable means for closing the contacts after the condition which causes the stoppage is corrected. However, after pressure is reestablished in the fluid line, it is necessary for the operator to manually release the resetting means so that the contacts are free to automatically open again if and when the pressure drops. In the event that the operator forgets to release the device, the switch is completely inoperative and will fail to perform its function.

It is therefore the main object of the present invention to provide a resetting device which automatically disengages when the switch is in its normal position, so that said switch is free to act when the predetermined event again takes place.

Another object of the invention is the provision of a resetting device which is economical and simple to construct and effective under all conditions.

Other objects and advantages will be seen from the following specification and from the drawings therein:

Fig. 1 is a vertical cross sectional view through a fluid pressure responsive switch showing the present invention.

Fig. 2 is a top plan view of the switch with the housing top removed.

Fig. 3 is a horizontal cross sectional View through the switch housing at a point under the switch arm showing the invention in an inoperative position.

Fig. 4 is a side elevational view of the switch housing showing the action of the weighted portion of the resetting means.

Fig. 5 is a cross sectional view through a switch housing showing a modified form of the invention.

Fig. 6 is a greatly enlarged, semischematic cross sectional view of the preferred form of resetting means showing the same in cooperation with the switch arm.

Fig. 7 is a view similar to Fig. 6 showing still another modified form of the invention.

The preferred form of the invention, illustrated in Figs. l-4 and 6, is shown in use with a switch substantially similar to that disclosed in the above mentioned copending application.

In detail, the switch comprises an upright housing generally designated I which is provided at its lower side with an internally threaded hole 2 for receiving therein a pipe which, in turn, is connected to the pressure side of the pump that it is desired to control.

A diaphragm 3 is provided which is adapted to deflect upwardly when fluid pressure is applied to its lower side. On diaphragm 3 is a switch arm actuating member 4 which engages the underside of switch arm 5 and swings the latter upwardly when pressure is applied to the diaphragm 3.

Switch arm 5 is pivotally supported at one end on the housing I by means of a pair of downwardly projecting pivot knobs 6 and is provided at its other end with contacts 1 arranged on a bar 8 which, in turn, is urged upwardly at all times by a helical compression spring 8. The spring 9 surrounds a headed pin I0 which is fastened at its lower end to switch arm 5.

Stationarily secured on a fixed insulating bar I2 above the switch arm 5 are a pair of fixed contacts I3 which are adapted to be engaged by contacts I on the swingable switch arm 5 when the latter swings upwardly. Fixed contacts I 3 are provided with binding posts I5 to which the wires I6 may be secured in the usual manner. When the device is used as a safety switch to prevent a motor driven pump from running dry, the fixed contacts I2 are in series with the motor circuit so as to start and stop said motor as required.

The switch arm 5 is urged downwardly at all times by a helical compression spring I1 which acts on said arm adjacent its pivoted end (Fig. 1)

At this point the general operation of the switch may be briefly described.

Upon fluid pressure being applied to the underside of diaphragm 3, the same deflects upwardly and swings the switch arm 5 clockwise about its pivots 6 so that moveable contacts I engage the fixed contacts I3 to close the circuit which includes said fixed contacts I3. As long as the pressure on diaphragm 3 does not drop below a predetermined pressure, the circuit remains energized. However, if the pressure drops, the diaphragm deflection is not suflicient to hold the switch arm up against the urging of spring I! and said am swings downwardly (counterclocl wise) and the contacts I3, I7 open, stopping the motor, and preventing the pump from running dry.

When it is desired to again energize the motor it is necessary to manually close the contacts I3,

I! by swinging switch arm upwardly. The engagement of contacts l3, I! must be maintained until pressure is reestablished against diaphragm 3. Inasmuch as attainment ofithesproper pres sure may take.- considerable time (especially if the pump must be primed) it is necessary to hold the contacts closed while the operator concerns him self with other matters.

The present invention provides a" resetting means for achieving this result.

Extending transversely of the switch arm 5 and under the latter is a shaft' fll' which isro tatably supported adjacent its opposite ends? in the housing I. As best seen in Fig. 3, the shaft is provided, intermediate its ends, with a pair of radially outwardly extending projections 21 which are adapted to engage the-switch arm" 5 when swung counterclockwise from'the position of Figs; 1, 3, 4. In addition, projections 21 posi= tively swing switch arm 5 upwardly to the dotted line position of Fig. 1 so that" contacts-7', l3' are engaged; It should be noted in this connection that the compression spring S-permits the switch arm 5*to' overtravel the point at which the contacts T, l3' first engage, and this is desirablebe cause the contacts T, |3-'are thus held together" under yieldable pressure.

Atone end of the shaft 20 and outside"hous ing If the shaft 20 is provided witharelatively heavy eccentric portion 23 (Figs. 2, 3, 4, 6) which tends, atall times, to swing theshaftZit-c-lock wise as seen in Figs.- 1, 4 and out ofengag'ement with the switch arm 5. However, when the" shaft 2a is rotated counterclockwise (Fig. l) to close contacts 1; I3, it frictionally engages the switch arm 5 so as to hold-the shaft"'2l'l andarm- 5' in the relative positions illustratedfin run line in Fig. 6. In other words; thetorque onshaft 20'iexerted by weighted p'ortion 23 is' not nor-- mally suflieient to overcome the-friction between projectionsZl and switch arm 5 which-virtuallyholds the shaft 20 and arm5 ina-lockedposi tion.

The upper, or operative position of "projections 2! is preferably suchthat a-line betweenthe point of engagement between projections 21 and arm 5" and the center of: rotation-of shaft-2i) makes an angle'iof slightly. less than 90" degreeswith. the horizontal; If such anglewere equal to or. exceeded a rightiangle, there would he no tendencyfor the: shaftto rotate clockwise'unden the torque impartedby'weighted portion 2 -3*-'un"-- less the weight 'of' said portion were extremely great and the disposition ofith'e "eccentric" weight accurately taken" into account.

hold it there by-friction. The motor .is-thus'en-l ergized and the pump, operatestc' -build .up; press sure against diaphragm 3';

However, after resetting: the 'switch; thef opera tor is free to clear away any obstructions in the suction-line of? the" pump-, prime the pump; or take whateverrother: action: is requiredt When working pressure is again reestablished against diaphragm 3, the member 4 engages switch arm 5 and swings the sam further in a clockwise direction against the resistance of spring 9: Further upward'swinging ofsWitch arm 5 reduces or eliminates the frictional force existing between projections 2i and switch arm 5 (Fig. 6) thus permitting the shaft 29 to swing clockwise under the torque'existing-b'y virtue of the eccentric weighted portion 23;-

If, for any reason, pressure is reduced below apredetermined" minimum the switch arm 5 is free to swing downwardly to disengage contacts I and I3 and thus breale the motor circuit.

A somewhat different form of the invention is shown in' Fig. 5" wherein a" switch arm 30" of a different type'isadaptedto' swing about a pivot 31" for urging movable contacts 32" into engagement with fixed contacts33. arm" engaging member B l/is adaptedtc swingthe' switch arm"30 counterclockwise for engaging contacts" 32, 33'. In this case theportion'of swit'ch'arm' 38 that is provided with'conta'cts' 32is disposed"vertically,v but it will be understoodthat the general operation is the same.-

Pivotally secured to switch arm 30is' one end" of an elongated-link 35 which is provided with an upwardly opening notch 36% IJink'35'is vertically slidable within a vertically extending slot 31' in the adjacent sidewallts of the switchhousing and'the-notch'36 is adapted to receive the-upper margin of slot 37 asseen'in dotted line "in Fig; 5'.

When link 351s in said dotted-position and the contact points 32 33*ar'e in engagement; itwill be apparent, uponupward deflection of'the diaphragm that the-frictional grip between'n'otch SB' and the sidewall 38* of the housing will here duced permitting'link 35to' drop downwardly to itsfull line position.

As in thecase of the previously described"struc-' ture, thecontacts 32; 33 'will then be'permittedtoopen-when pressure is'reducedan'd switch arm 30 swings clockwise.

It Will be noted that the force of gravity is-employedin the above described cases-to return the resetting device to an inoperativeposition-once the pressure-has been reestablished.

The present-invention alsocontemplates theuse of a spring or the like to apply the unb'alancing iforce as= illustrated-in Fig. 7.

The structure disclosedschematically I in Fig: 7 Y is similar tothat shown in- Figspl-l and 6 ex cept that the switch arm 40 is providedw-ith' spring means for urging the same 'upWardlyat'all times to open thecontacts; The shaf't 4 l corre-' sponding to shaft 26 in Figs. 1-3 and 6 is swung downwardly intofriction-al engagement with switch'erni'dll and isurgedupwardljr at all times by an extension spring d2 whichmaybesecured toenyconvenient fixed structure d3:

Upon downward movement" of switclf' arm 481" to reduce the friction betwe'en'th'e same'andshaft H; thesprin'gZ "pulls the shaft sl clockwis'eirit'o' inoperativepositionarid thus permits the switch arm ll! to move upwardly. to open thecontact's when-the fluid pressure fallsbelow the predetermined" minimum.

The present invention should'n'ot' be under-'- I claim:

1. In a switch, a member having a moveable electrical contact thereon adapted to engage a fixed contact upon movement of said member toward the latter, means for urging said member away from said fixed contact at all times for opening the circuit which includes said contacts, a resetting element for spacing said member a predetermined distance from a fixed point and releasably held in spacing position by friction, thereby engaging said contacts and closing said circuit, means for urging said element to a position out of frictional engagement at all times whereby said element moves to said position when said member is moved toward said fixed contact to reduce the friction of said frictional engagement.

2. In a switch, a member having a moveable contact thereon adapted to engage a fixed contact when said member is moved toward said contact to a closed position, means for urging said memher to an open position at all times for disengaging said contacts to open the circuit which includes said contacts, a resetting element for holding said member in said closed position and moveable from an operative position in which said member is so held by friction to an inoperative position permitting said member to be moved to an open position by said means, means for urging said element to said inoperative position at all times against said friction whereby said element moves to said inoperative position when said member is moved toward said fixed contact to reduce said friction.

3. In a switch, a member having a moveable contact thereon adapted to engage a fixed contact when said member is moved toward said contact to a closed position, means for urging said member to an open position at all times for disengaging said contacts to open the circuit which. includes said contacts, a resetting element for holding said member in said closed position and moveable from an operative position in which said member is so held by friction to an inoperative position permitting said member to be moved to an open position by said means, means for urging said element to said inoperative position at all times against said friction whereby said element moves to said inoperative position when said member is moved toward said fixed contact to reduce said friction, said last mentioned means comprising a weight carried by said element for unbalancing the latter when in said operative position.

4. In a switch, a member having a moveable contact thereon adapted to engage a fixed con tact when said member is moved toward said contact to a closed position, means for urging said member to an open position at all times for disengaging said contacts to open the circuit which includes said contacts, a resetting element for holding said member in said closed position and moveable from an operative position in which said member is so held by friction to an inoperative position permitting said member to be moved to an open position by said means, means for urging said element to said inoperative position at all times against said friction whereby said element moves to said inoperative position when said member is moved toward said fixed contact to reduce said friction, said element being supported for swinging into frictional engagement with said member and for urging the 5 latter toward said fixed contact and to said closed position.

5. In a switch, a member having a moveable contact thereon adapted to engage a fixed contact when said member is moved toward said contact to a closed position, means for urging said member to an open position at all times for disengaging said contacts to open the circuit which includes said contacts, a resetting element for holding said member in said closed position. and moveable from an operative position in which said member is so held by friction to an inoperative position permitting said member to be moved to an open position by said means, means for urging said element to said inoperative position at all times against said friction whereby said element moves to said inoperative position when said member is moved toward said fixed contact to reduce said friction, said element being pivotally secured at one end to said member and engageable with a fixed abutment at its opposite end.

6. In a switch, a member having a moveable contact adapted to engage a fixed contact when said member is moved toward said contact to a closed position, means for urging said member to an open position at all times for disengaging said contacts to open the circuit which includes said contacts, an element swingably supported at one end for engagement of its opposite end with said member for urging the later to said closed position with said opposite end of said element in frictional engagement with said member, said element being formed with a weighted portion eccentric to said one end for urging said element away from said member against the resistance of the friction between said element and said member whereby said element swings away from said member by gravity when the latter is urged toward said fixed contact while in said closed position.

7. In a switch having a fixed contact and a moveable contact adapted to be engaged and disengaged for making and breaking a circuit which includes said contacts, a member supporting said moveable contact for movement between engaged and disengaged positions, a pressure actuated diaphragm connected with said member for moving it toward said fixed contact to make said circuit when a predetermined fluid pressure is applied to said diaphragm, an element swingably supported at one end for engagement of its opposite end with said member for urging the latter toward said fixed contact to an engaged position with said opposite end of said element in frictional engagement with said member, whereby said contacts are closed by said element when said fluid pressure is less than said predetermined amount, means for urging said element out of engagement with said member at all times against the force of friction between said element and said member whereby said element is released from said member when said fluid pressure exceeds said predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,287,522 Torgersen Dec. 10, 1918 1,361,263 Jacobsen Dec. 7, 1920 1,658,342 King Feb. 7, 1928 1,723,996 Ackerman Aug. 13, 1929

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