US2599657A

US2599657A - Electrical switch mechanism

Info

Publication number: US2599657A
Application number: US148317A
Authority: US
Inventors: Pavitt Frederick James
Original assignee: Allen West and Co Ltd
Current assignee: Allen West and Co Ltd
Priority date: 1949-02-28
Filing date: 1950-03-08
Publication date: 1952-06-10
Anticipated expiration: 1969-06-10
Also published as: GB661222A

Description

June 10, 1952 J PAVlTT 2,599,657

ELECTRICAL SWITCH MECHANISM Filed March 8, 1950 5 Sheets-Sheet l lllllmllmmllll 30' p 3 Al'o ey June 10, 1952 VlTT 2,599,657

ELECTRICAL SWITCH MECHANISM Filed March 8, 1950 a Sheets-Sheet 2 Inventor June 10, 1952 F. J. PAVITT ELECTRICAL SWITCH MECHANISM 3 Sheets-Sheet 3 Filed March 8, 1950 Inventor EVZ'ZLLL By 4.

A or ey patented June 10, 1 952 UNITED STATES PATENT OFFIEE Frederick Mines l aeitt, Brighton,

signofr t6 Allen West and Company Limited,

Brighton,-'England, a British company Am li i i March 8; 1950,, serial/f.

I171 G eat Britain uar 28; ,1}?

(Ci. Mme-406) 13Clail'ii5'.

This invention relates to eiecti'icai switch mechanism and has for its obiebt to pi'otii'dje an improved electrical switch mechanism of the kind which can be closed manually, tripped with a snap action manually, and tripped with a snap' aetion under faulty electric conditions independently of any man la] operation.

The invention consists broadly of an ele'etri cal switch mechanism comprising a movableswitch element movable in one direction to the closed position of the switeh and in the other qirection to the open position of the switch and biased-tome open position of said switoh,

an' actua'ting element movable to an operative position anti returnable to a non epe'ratii e positi'on; a lever pivotably mounted between its entis' onsa'id aeti 'ating element, a tripping ele-- ment 'whieh is positioneei according to the elec-' trical conditionsfin thecireuit eontrplle'd by said switch, said; tripping element having a no fn al' p'o'sitior whioh it beoup'ies when said circuit conditions alitfi f l l Ql ma'l' and -a tripping Dosition whic'h -it open Les when said ci'riiit on 'en ar ab mal y the ef t e m h i ing such that, when said actuating eleii ent is moved to the operative position, said tripping element, tang at the no 'fnai position; jretains one end of said ie' vei' whereby "the otheii' end moves and engages said "switch element and conveys it'to the -ciosed position of the fiwi teh, and,-upon said tripping 1neving to the tripping position, *i't eieases the first-flamed end of said leven whereupon said switch 'elemerit-is {freeto -enim to the {open position oi. the svvi'teh thereby rotating the deter mm its pivot.

Tn order that-the invent-ion maybe the more clearly understood a=switch mechanis'm aeeo'rdance' therewith will -now =be described, reference being "made to the --accompanying =diaw in'gs wherein g Figure 1 is :a "front -e1e"vation'-o'f said me-ch III 2 partly insection-approximately on the line VII"- VII of Figure '3'; t Figure 8 is a fragmentary view showing certain of the parts when at the tripped position.

Referring to the drawings the switch is a three phase switch eeinprising three pairs of fixed contacts I and three bridging contacts 2. 'Ifhe bridging eontaetsf are mounted in spaced relation along contact carry ing bar 3 each bridging eontact being transverse to thebai and" projecting on each side thereof. sam a? s s iohgi-tudinaily' s ame to and from closed petition at which theend's of each bririg ing contact 2 engage its respeetiv'epair Qf'fixed e'entaets and a'iiflopenpo'sition .(illustrateii' in Figi'n'e 2) at whichle'a'eh' bridging contact 'dis= engages iespective pair of fixed contacts.

trip plate has "an arm 6 extending ni'oreeor eiess" horizontally irom' (one edge ith'ereoi. isaid p ate is pivoted at its opposite edge at J .50 that said arm 6 can -moive up anti f'down', means are previded,-{whiehwill be hereinaiiter deseiibed, iivhei'eby {so dong .as the windings" 4 are ene'i' gised but' notTovermaded .said .lrip piatea'i has its ari'n fi dQWmbixtiflah overload or voltage =-fai1=ure oecu rs in any mindihgkaiii tiip --piate is =r'alised to the up (position of isalid arm 6. Means are -.pi ovided, however, which will "be -hereinafter described, whereby" Inormally when the-switc'h is notiin iu'sei'said trip plate :5 -remains \with iitss'arin 16 at the aiiiwn position. I

A -sta' t Apiate ='8" is provide in 5a iveirtie'alp ajne parallelto-thepontaefiarryim barl3na'nd said start plate is horizontally siidableiniits own plane. Saidr'start Iate-sIi isiispringgbiased in the same :dire'etionaassaidehorikoiital -\;bar'=' 3, i.-e. to the- -i ight according toFigure'sB. anti-4.

-=A 'leve'r 9 is mounted Ion :said staftpIat 1'8 so' as to pivot about a -horizontal axis 10' ctr-ansverse to said sta'rt lplate. cSaict;1eirei$-9.;compiises a lon'garm extending upwardly.ltrom'itswpivot axism and said; long arm .at; its mpperiend sa tires 3 and 4) of the aforesaid arm 5 of the trip plate 5. Said lever 9 also comprises a short arm extending to the right from its pivot axis, and said short arm terminates in a downwardly extending hook portion 9b.

To close the switch, the start plate 8 is pushed to the left (according to Figures 3 and 4) in opposition to its spring bias. The upper end 9a of the lever 9 is retained by its engagement with the arm 6 of the trip plate 5, but

the lower end of said lever 8 is carried to the left with the start plate 8. When the start plate 8 has reached a given point in its travel to the left, the hook portion 91) of the lever 8 engages a horizontal lateral projection 3a from the contact-carrying bar 3, and thereafter said contact-carrying bar is carried to the left with said start plate. When the bridging contacts 2 have reached the closed position, said start plate 8 is latched against return.

The switch is now closed and the position is as in Figure 4. The long arm of the lever 9 is inclined to the right, and the short arm with the hook portion 53b is inclined downwardly. If overload or voltage failure takes place, the arm 6 of the trip plate 5 will be lifted, and will rise clear of the upper end 9a of the long arm of the lever 9. This leaves said long arm free to move to the left, and accordingly the short arm with the hook Sb to move to the right and upwards. Under the influence of the bias on the contactcarrying arm 3 this movement of the lever 9 takes place until the hook portion 91) is clear of the lateral projection 35:. on the contact-carrying bar 3, whereafter said contact-carrying bar springs freely to the fully open position of the switch. The lever 9 is now at a limiting position with its long arm inclined to the left and its short arm with the hook Qb inclined upwards. The start plate 8 is still latched at its left-hand position of Figure 4. The relationship of the lever 9 and the lateral projection 3a is as shown in Figure 8.

The means by which the trip plate 5 is lifted in response to either overload or voltage failure may be substantially the same as those described on my prior Patent No. 2,431,886 granted December 2, 1947. That is to say the windings 4 have dash pot controlled plungers H which are lifted by overload and thereby lift said trip plate 5 which overlies them, and also have no-volt armatures I2 which rise under spring bias under conditions of no-voltage and thereby, again, lift said trip plate 5 which overlies them.

In order that the trip plate 5 shall remain at the down position when the switch is not in use, a pivoted holding plate i3 is provided pivoted about the same axis I as the trip plate. This holding plate overlies the no-volt armatures l2 and is normally spring biased downwardly so as to hold said no-volt armatures down against their bias when the switch is not in use.

The means for latching the start plate 8 at its left-hand position consists of a stop-and-reset element M which pivots about a fixed axis it transverse to the plane of said start plate. This stop-and-reset element has two arms Ilia, Mb projecting to the left one above the other and it is biased clockwise, i. e. the said arms are biased upwards. The start plate at its upper edge has a horizontally bent-over lug 8a which overlies the upper edge of the lower arm Mb of the stop-andreset element l4 and thereby limits the clockwise movement of the latter. The upper arm of said stop-and-reset element is immediately underneath the holding'plate l3. Said stop-and-reset element also carries a leaf spring 16 projecting to the left above the holding plate.

When the start plate 8 is at its oif or righthand position, said bent-over lug Ba of said start plate retains said stop-and-reset element so far counter-clockwise that its upper arm is clear of the underside of said holding plate l3 and said spring l6 presses said holding plate to the down position. This is the position of Figure 3. When the start plate 8, in moving to the left, reaches the closed position of the switch said bent-over lug 8a reaches a downwardly stepped portion Mc of the lower arm of said stop-and-reset element M, and consequently the latter is capable of rotating a given distance in the clockwise direction to the position of Figure l. The start plate 8 is now latched by the step at Me against return movement, and also the spring it has moved clear of the holding plate 13 and the upper arm I ia of said stop-and-reset element has moved far enough up to lift said holding plate clear of the n-o-volt armatures. Thus, the no-volt armatures I2 are free to lift the trip plate 5 and cause the same to exercise its tripping function and, at the same time, the start plate 8 is latched at its left hand position. It will be seen that if, in the interval subsequent to the closure of the switch contacts I, 2 and prior to the release of the no-volt armatures i2, a heavy overload should occur, the overload plungers I! will be free to rise and lift the trip plate, despite the fact that the no-volt armatures are still held down.

Assuming that the switch has been tripped by overload or phase failure as heretofore described, the starting plate 8 will be still latched at the position of Figure 4 and. the correlation of the lever 9 and the projection 3a will be as in Figure 8. In order to reset the mechanism for enabling the switch to be again closed, said stop-and-reset element i i is rotated counter-clockwise by hand. This moves the step 140 on the lower arm 14b of said stop-and-reset element clear of the bentover lug 80. on the start plate 8, so that the latter can spring back to the right-hand position. At the same time the upper arm Ma of the stop-andreset element i4 and also the spring I6 move down and the holding plate is again returned by the spring iii to its down position, and, the bentover lug 8a on the stop plate being now at the right-hand position, the stop-and-reset element It will be prevented from returning clockwise, so the holding plate will remain down.

The start plate 8, in returning to the right, carries the lever 9 with it. Said lever first moves with its orientation unchanged (1. e. with its long arm inclined to the left and its short arm inclined upwardly) until the hook portion 9?) has passed over the lateral projection 3a on the contact-carrying bar 3. Just after this a downward tail projection at the lower end of said lever to the left of the hook portion 9b engages said projection 3a and consequently said lever 9 is turned in a clockwise direction about its pivot point Ill until its long arm is upright 0r inclined a little to the right and the short arm is horizontal or inclined a little downwardly. During this movement the upper end of said long arm rides under the arm 5 of the trip plate 5, temporarily lifting said arm 6. The hook portion 9b moves down into position to the right of the projection 3a on the contactcairrying bar 3. The switch is thus now fully rese Assuming that the switch is closed, to open it voluntarily the stop-and-reset element I4 is moved by hand counterclockwise as before, and

this, as before, win o'er it the start plate..8 to spring back to the right hand position, and win cause the holding plate I3 to be pressed down by means of the spring it. As this latter takes place be'forethe switch contacts I and 2 o'p'en there is no moment when the trip plate 5' is lifted. Consedue'ntly the upper end So of the long arm of the lever 9 remains to the right of the arm 6 of the trip'plat'e, and the contact-carrying arm 3simply moves to the right with the hook portion tbof the lever. Thus the whole mechanism is set for re closure by'the start plate 8.

Describing how certain constructional details of the invention the fixed contacts I are mounted on ajmain body I? of insulating material. The contacts I of the bottom row pass through to the front of the body ll where they are fitted with connecting screws. H3. The contacts l' of the top row are electricallyconnected to terminals It at the back or said body 51. Other terminals are inounted at' the back of said body side by side' with the contacts I of the bottom row. These terminals 26 pass through to the front of said body where they are fitted with connecting screws 2i. Ihe windings 4 are connected across the .respective pairs of connecting screws I8 and 2| at the front of the body ll, by conductors 22 one of which is seen in Figure 5, and it will be seen that by connecting the respective pairs of terminals l8 and 20 at the back of said body in the three phases of the controlled circuit; circuit con"- nections will be completed through the windings 4 when the bridging contacts 2 are moved to the bridging position in contact with the contacts I.

The contact-carrying bar 3 is slidable-in a guide groove in the back of the body H. The biasing of said bar 3 to the open position of the contact 2 is effected by means of a coiled torsionlspring 23 mounted in a recess in the front of said body IT and having an extending arm 23a which engages the end of said bar 3, as shown in

Fi ures

2, 3 and e. As shown in Figure 2 the arm 23a hooks round the end of said bar 3} and thus serves to retain that end of said bar within its guide groove. For retaining the other end of said bar in its guide groove, the start plate, which slides against the front face of said body l'l, hasa rear tail extension 8b which passes round from the front to the back" of said body where it overlaps said bar 3 asbestshown in Figure 2.

The'start plate t" is guided inits-sliding more rnent against the front face of the body I? by means of locating studs 2s and 25' on" said front face'engaging in cut -

outs

28 and 27 in said start plate,- and also by the tail extension B'b' engaging in'a groove 23 in'the front face of said body; Said start plate is retained against said-front face of said body by means of a plate 2'9 secured against the front face of the body.

The plate 29 carries thethree windings t togetlier with the overload plungers H, the novolt armatures l2 and the dash pots Si! by which said overload plungers are controlled. The'structurecarried by said plate 25 is substantially as described in my Patent No. 143L886 aforesaid andformsjin itself, no part of the present invention. It is sufiicient to say that the vertical plates 31" are rigidly mounted in front of the windings Q-and that the no-volt armatures I2 arepivoted on the upper'edg-es of said plates 3| and have tail extensions 32 which are biased downwardly by means oftension springs 33 whose upper ends are connected to said tail extensions and whose lower ends are connected to points near the lower ends" or said' plates-i Thus the" xiii-volt armatures 6 themselves are biased upwardly, and move-up;- wardly upon the occurrence of voltages failure: The overload plungers H are biased downwardly by gravity and are raised upon the occurrence of overload.

The pivot axis 1 of the trip plate 5 soothe holding plate I3 is constituted bya' length ofwire carried by the body I! as will b clea'r from the drawing. The arm 6 of said trip plate overlies the plunger H and no-volt armature [2 of the centre winding t, and, in addition there are we

other arms

34 and 35 which overlie'the plung s II and no-volt armaturs l2 of the other wi" ings A. Thus, as before stated; the trip plat 5 is lifted upon the rising of any'of the overload plungers or any of the no volt armatures.

A common horizontally arranged tension can spring so serves both to bias the start plate ilto its right hand position (according to Figures stop and reset element M in the and 4) and the clockwise direction. This spring 3'S'fat its' left' hand end is connected (as best shown in Figures 3 and i) to the forward end of the start plate8; and, at its right hand and to the bottom of the stop-and reset element l4. p g

The lever 52 is guided in its travel byflbeing mounted between the s'tartplate 3 and th'e froiit face of the body it. The stopand-reset element is mounteiion the body :7 as will be' iear' frdifi' the drawing. It consists ofa plate bentiri plan to U form, the arm Ma being on one side of the U and the arm i on the'otlier.

In practice the whole mechanism may be e closed in a casing (not shown) which has" two push buttons mounted in one of its walls; start push button which, on depression,- presses the start plate to the left by engaging the tail extension db, and a stop and-rese't push button which on depression engages the stop-and r'ese't element is and rotates it counter-clockwise.

I claim:

1. An electrical switch mechanism comprising an actuating element movable to an operative position and returnable to a non oper'ative' position, a lever pivotably mounted between its ends on said actuating element, a switch elementniovable along a given path in one direction to a s'witcli closing position and in the other direction to a.

switch opening position, means biasing said switch element to said switch-opening position; a tripping element having a normal position a tripping position, means for maintaining said tripping element at saidnormal position in re sponse to the electrical conditions in the circuit controlled .by said switch being normal; and for moving said tripping element to said tripping p'o? sition in response to said electrical conditions being abnormal, said tripping element, at its nor mal position, being located to engage and retain one end of said lever, upon said actuating element being moved from its inoperative to its' operative position, whereby the other end of saidle'ver is moved, and said other end being locatedto' en gagesaidswitch' element by such movemehtand convey it to the switch closing position, and said tripping element; upon'moving to the tripping position, disengaging and releasing the first named end of said 1ever,- whereby said switch elee ment' is returned by said biasing means to said switch-opening position.

2. An electrical switch mechanism comprising an actuating element movable to an op'erativeposition and returnable to" a non-operative position; a lever pivotably mounted between, its ends on said" actuating element; a switch elementmounted independently of said lever for movement along a given path in one direction to a switch closing position and in the other direction to a switch opening position, means biasing said switch element to said switch-opening position, a tripping element having a normal position and a tripping position, means for maintaining said tripping element at said normal position in response to the electrical conditions in the circuit controlled by said switch being normal, and for moving said tripping element to said tripping position in response to said electrical conditions being abnormal, said tripping element, at its normal position, being located to engage and retain one end of said lever, upon said actuating element being moved from its inoperative to its operative position, whereby the other end of said lever is moved, and said other end being located to engage said switch element by such movement and convey it to the switch closing position, and said tripping element, upon moving to the tripping position, disengaging and releasing the first-named end of said lever, whereby said switch element is released by said other end and returned by said biasing means to said switch-opening position.

3. An electrical switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative posi-= tion, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a lever plvotably mounted between its end on said actuating element, a switch element movable along a given path in one direction to a switch closing position and in the other direction to a switch opening position, means biasing said switch element to said switch-opening position, a tripping element having a normal position and a tripping position, means for maintaining said I tripping element at said normal position in response to the electrical conditions in the circuit controlled by said switch being normal, and for moving said tripping element to said tripping position in response to said electrical conditions being abnormal, said tripping element, at its normal position, being located to engage and retain one end of said lever, upon said actuating element being moved from its inoperative to its operative position, whereby the other end of said lever is moved, and said other end being located to engage said switch element by such movement and convey it to the switch closing position, and said tripping element, upon moving to the tripping position, disengaging and releasing the firstnamed' end of said lever, whereby said switch element is returned by said biasing means to the switch-opening position.

4. An electrical switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a lever pivotably mounted between its ends on said actuating element, a switch element movable along a iven path in one direction to a switch closing position and in the other direction to a switch opening position, means biasing said switch element to said switch opening position, a tripping element having a normal position and a tripping position, means for maintaining said tripping element at said normal position in response to the electrical conditions in the circuit controlled by said switch being normal, and for moving said tripping element to said tripping position in response to said electrical conditions being abnormal, said tripping element, at its normal position, being located to engage and retain one end of said lever, upon said actuating element being moved from its inoperative to its operative position, whereby the other end of said lever is moved, and said other end being located to engage said switch element by such movement and convey it to the switch closing position, and said tripping element, upon moving to the tripping position, disengaging and releasing the first-named end of said lever, whereby said switch element is returned by said biasing means to the switch-opening position, and means whereby, upon said actuating element, subsequently to the return of said switch element to the switch opening position in response to abnormal circuit conditions, returning to the non-=operative position under its spring bias in response to the release of said latch, said other end of said lever engages said switch element, whereby said lever is returned to the position for its first-named end to engage said tripping element upon said actuating element being again moved to the operative position.

5. An electrical switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a lever pivotably mounted between its ends on said actuating element, a switch element movable along a given path in one direction to a switch-closing position and in the other direction to a switchopening position, means biasing said switch element to said switch-opening position, a tripping element having a normal position and a tripping position, means for maintaining said tripping element at said normal position in response to the electrical conditions in the circuit controlled by the switch being normal, and for moving said tripping element to said tripping position in response to said electrical conditions being abnormal, said tripping element, at its normal position, being located to engage and retain one end of said lever upon said actuating element being moved from its inoperative to its operative position, whereby the other end of said lever is moved, first and second projections formed on said other end of said lever, said first projection being located to engage said switch element, by such movement of said other end of said lever, and convey said switch element to the switch closing position, and said tripping element, upon moving to the tripping position, disengaging and releasing the first-named end of said lever, whereby said switch element is released by said first projection and is returned by its biasing means to said switch-opening position, and means whereby, upon said actuating element, subsequently to the return of said switch element to the switch opening position in response to abnormal circuit conditions, returning to the non-operative position under its spring bias in response to the release of said latch, said second projection engages said switch element, whereby said lever is returned to the position for its first-named end to engage said tripping element upon said actuating element being again moved to the operative position.

6. An electrical switch mechanism comprising an actuating element movable to an operative tion, means biasing said actuating elementto'said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a lever piviotably mounted between its ends on said actu- Iating element, a switch element-movable along a given path in one direction to a switch closing position and. in'the other direction to a switch opening position, means biasing said switch element to said switch opening position, a tripping element having a normal position and a tripping position, means for maintaining said tripping element at said normal position in response to the electrical conditions in the circuit controlled by said switch being normal, means for moving said tripping element to said tripping position in response to no-volt conditions in said circuit, means controlled by said latch for preventing such movement of said tripping element in response to such no--volt conditions when said latch is at its normal non-latching position and for permitting such movement when said latch is latching said actuating element at its operative position, said tripping element, at its normal position, being located to engage and retain one end of said lever, upon said actuating element being moved from its inoperative to its operative position, whereby the other end of said lever is moved, and said other end being located to engage said switch element by such movement and convey it to the switch closing position, and said tripping element, upon moving to the tripping position, disengaging and releasing the first-named end of said lever, whereby said switch element is re= leased by said other end and returned by its bias ing means to said switch opening position.

7. An electric switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position,

means biasing said actuating element to said nonoperative position, a manually releasable latch for automatically latching said actuating element at said operative position, a switch element movable along a given path in one direction to a switch closing position and in the other direction to a switch opening position, means biasing said switch element to said switch opening position, transmission means whereby movement of said actuating element to said operative position eifects movement of said switch element to said switch closing position, a no-volt armature, a winding for said no-volt armature in the circuit controlled by said switch, said winding when energised maintaining said armature at an attracted position, means biasing said no-volt armature to the non-attracted position, means for tripping said transmission means in response to movement of said no-volt armature to the non-attracted po= sition, and thereby permitting said switch element to return to the switch-opening position, and means controlled by said latch for preventing movement of said no-volt armature to the nonattracted position when said latch is at its normal non-latching position and for permitting such movement when said latch is latching said actu ating element at said operative position.

8. An electric switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a switch element movable along a given path in one direction 10 to a switch, closing position and in the other direction to a switch opening, position, means biasing said switch element to said switch opening position, transmission means whereby movement ofsaid actuating element to said operative position effects movement of said switch element to said switch closing position, a winding'in the circuit controlled by said switch, a no-voltiarmature for said winding having'an attracted and a non-attracted position and biased to its nonattracted position, an overload'armature for'isaid winding having an attracted and a non-attracted position and biased to its non-attracted position,

winding whenncrmally energised maintaining said no-volt armature at its attracted position and leaving said overload armature at its non-attracted position, and, when energised by overload, moving said overload armature to the attracted position, means for tripping said'transmission means in response to movement'of said no-volt armature to the non-attracted position or movement of said overload armature to the attracted position, and thereby permitting said switch element to return to the switch opening position, and means controlled by said latch for preventing movement of said nc-volt armature to the non-attracted position when said latch is at its normal non-latching position, and for permitting such movement when said latch is latching said actuating element at its latching position, said last-named means in no circumstances preventing movement of said overload armature to its attracted position.

9. An electric switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a switch element movable along a given path in one direction to a switch closing position and'in the other direction to a switch opening position, means biasing said switch element to said switch opening position, transmission means whereby movement of said actuating element to said operative position effects movement of said switch element to said switch closing position, a winding in the circuit controlled by said switch, a no-volt armature for said winding having an attracted and a non-attracted position and biased to its nonattracted position, an overload armature for said winding having an attracted and a non-attracted position and biased to its non-attracted position, said winding when normally energised maintaining said no-volt armature at its attracted position and leaving said overload armature at its non-attracted position, and, when energised by overload, moving said overload armature to the attracted position, a tripping element having a normal position and a tripping position, said tripping element, when at its tripping position tripping said transmission, means and thereby permitting said switch element to return to the switch opening position, means whereby move ment of said no-volt armature to the non-attracted position or movement of said overload winding to the attracted position, efiects movement of said tripping element to the tripping position and means controlled by said latch for preventing movement of said no-volt armature to the non-attracted position when said latch is at its normal non-latching position, and for permitting such movement when said latch is latching said actuatin element at its latching position,

said last-named means in no circumstances preventing movement of said overload armature to its attracted position.

10. An electrical switch mechanism comprising a switch element movable in one direction to a switch-closing position and in the other direction to a switch-opening position, means biasing said switch element to said switch opening position, an actuating element movable to an operative position and returnable to a non-operative position, transmission means whereby movement of said actuating element to said operative position effects movement of said switch element to said switch closing position, a winding in the circuit controlled by said switch, a no-volt armature for said winding having an attracted and a non-attracted position and biased to its nonattracted position, an overload armature for said winding having an attracted and a non-attracted position and biased to its non-attracted position,

said winding when normally energised maintaining said no-volt armature at its attracted position and leaving said overload armature at its non-attracted position, and when energised by overload, moving said overload armature to the attracted position, a tripping element having a position for tripping said transmission means, said tripping element being actuated to the tripping position by movement of said no-volt armature to the non-attracted position or movement of said overload armature to the attracted position and thereby permitting said switch element to return to the switch-opening position, a separate holding element, and an interlock between said actuating element and said holding element whereby said holding element engages said novolt armature and holds it at the attracted position for all positions of said actuating element except said operative position and releases said no-volt armature at said operative position of said actuating element, said holding element at no time obstructing movement of said overload armature to its attracted position.

11. An electric switch mechanism comprising an actuating element movable to an operative position and returnable to a non-operative position, means biasing said actuating element to said non-operative position, a manually releasable latch for automatically latching said actuating element at said operative position, a switch element movable along a given path in one direction to a switch closing position and in the other direction to a switch opening position. means biasing said switch element to said switch opening position, transmission means whereby movement of said actuating element to said operative position efiects movement of said switch element to said switch closing position, a winding in the circuit controlled by the switch, a no-volt plate armature at one end of said winding biased to a non-attracted position away from said winding, an overload plunger armature within said winding biased to a non-attracted position in the opposite direction to said no -volt plate armature, said winding, when normally energised maintaining said no-volt armature in opposition to its bias at an attracted position and leaving said overload plunger armature at its non-attracted position, and when energised by overload moving said overload plunger armature through an opening in said no-volt plate armature to an attracted position, a tripping element having a normal position and a tripping position, said tripping element, when at its tripping position tripping said transmission means and thereby permitting said switch element to return to the switch opening position, means whereby, either said no-volt plate armature in moving to the non-attracted position or said overload plunger armature in moving to the attracted position engages said tripping element and moves it to the tripping position, and means controlled by said latch for preventing movement of said no-volt armature to the non-attracted position, when said latch is at its normal nonlatching position, and for permitting such movement when said latch is latching said actuating element at its latching position, said last-named means in no circumstances preventing movement of said overload armature to its attracted position.

12. An electrical switch mechanism as claimed in claim 10, comprising a pivoted element constituting said interlock, said pivoted element having a first position at which it holds said holding element at the position for holding said no-volt armature at the attracted position, and a second position at which it releases said holding element, and means biasing said pivoted element to said second position, said actuating element engaging said pivoted element to hold the same at said first position at all positions of said actuating element except said operative position and to permit said pivoted element to move under said bias to said second position at said operative position of said actuating element.

13. An electrical switch mechanism as claimed in claim 12, wherein said actuating element is formed with a shoulder and said pivoted element in moving to said second position engages said shoulder to obstruct return of said actuating element to its non-operative position.

FREDERICK JAMES PAVITI.

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

UNITED STATES PATENTS Number Name Date 986,708 Greene Mar. 14, 1911 1,292,651 Rippl Jan. 28, 1919 2,431,886 Pavitt Dec. 2, 194'? 2,483,645 Kitman Oct. 4, 1949 FOREIGN PATENTS Number Country Date 814,480 France Mar. 22, 1937