US2816987A - Overload tripping switch - Google Patents

Description

Dec. 17, 1957 8 Sheets-Sheet 1 Filed Dec. 22. '1954 Dec. 17, 1957 E. J. HAGDAHL 2,816,987

OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 2 Dec. 17 1957 J HAGDAHL' 2,816,987

OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 3 IN Max/70R H/VJT .7556? #6 60904 1957 I E. J. HAGDAHL ,816,

OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 4 HTroRzwF) Dec. 17, 19.57 E.J. HAGDAHL 2,816,937

' OVERLOAD TRIPPING swI'rc'H Filed Dec. 22. 1954 8 Sheets-Sheet 5 Dec. 17, 1957 E. J. HAGDAHL 2,816,987

OVERLOAD TRIPPING swncn Filed Dec. 22. 1954 a Sheets-Sheet 6 ,ar WN flrromvir Dec. 17, 1957 E. J. HAGDAHL OVERLOAD TRIPPING SWITCH 8 Sheets-Sheet 7 Filed Dec. 22. 1954 IN VE/V To R 7 JEN/0N 170004111.

,QrrQRNEY Dec. 17, 1957 E. J. HAGDAHL 2,816,937

OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 s Shegts-Sheet s firv-omver United States Patent OVERLOAD TRIPPING SWITCH Ernst Johan Hagdahl, Bromma, Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a corporation of Sweden Application December 22, 1954, Serial No. 476,955 Claims priority, application Sweden January 13, 1954 4 Claims. (Cl. 200-116) This invention relates to an overload tripping switch of the type in which the operating system consists of a kneejoint mechanism whose motion can be controlled either by a manually adjusted, operating member or by the motion of a member, sensitive to the action of heat, e. g. a bimetallic strip. With this type of switches the invention has the object to enable thatin case two-pole or multiple switching is wantedtwo or more switch-units may be joined together to a twoor multipole switch, each of said units consisting of a one-pole switch, in such a manner that, on occurring releasing in one of the one-pole switches, a release is automatically obtained in the remaining switches which are joined to said switch.

The invention will be described more in detail with reference to the accompanying drawings.

Fig. 1 shows on a large scale a switch viewed from the side with one side plate removed. Fig. lA-C shows the link mechanism shown in Fig. l in dilterent positions. Fig. 1D shows a part of the operating device in another position than that shown in Fig. 1.

Figs. 2, 4 and 10 correspond to Fig. l but are on a reduced scale, the parts, however, shown in Figs. 4 and 10 being shown in the position they have when the switch is in o position. Fig. 4A is a section taken along the line EE in Fig. 4. Figs. 3, 5, 6 and 7 are sections taken along the lines A-A, F-F, GG and D-D respectively in Fig. 2.

Fig. 8 is a side view of the switch with mounted side plate.

Fig. 9 is an enlarged elevational view of the movable and fixed contacts.

Fig. 11 shows, viewed from the front, three switches which form a unit. Fig. 11a shows a detail.

Fig. 12 is a section taken along the line HH in Fig. 2 whereby it is assumed, however, that three switches are placed side by side.

Fig. 13, A, B and C, show a blocking arm viewed from the side and the top respectively.

Fig. 14A and B show a link viewed from the front and the side respectively.

Fig. 15A and B show a connecting arm viewed from the side and the top respectively.

An embodiment of the one-polar switches of which the multipolar switch is built will firstly be described.

All components of the switch are mounted between two side plates 11 and 11a, plate 11 is bent at one edge 22 to form an L (Fig. 3). The turnable parts of the switch are carried by journals with bearings in the two side plates 11 and 11a. In Fig. 1 is shown the position of the various components when the switch is in the on position. The circuit for the current that is to be switched off is con nected to the terminals 1 and 7 and the current passes from the terminal 1 through a 'bimetal spring 2 and the terminal and through the switch operated contact arm 6 which is pivoted at its right end, the contact arm 6 (Figs. 1, 3 and 7) which is U-shaped in section being on either side provided with a tab 23 which rests in a slot 72 in a plate 71 of insulating material arranged on the inside of each side plate 11 and 11a respectively. Said slot 72 (Fig. 1) has a sloping edge at the top whereby the arm 6 can take the position shown by lines of dots and dashes in Fig. 1. The arm 6 is at its ends provided with contact members 6a and 6b which can be held against the fixed contact terminals 7 and 5.

The operating members of the switch comprise a rocker arm SE, 25, whereby 8 is the handle and 25 the lower part of the arm. The latter comprises two pieces of plate of the same shape which are parallel with each other. The rocker arm is pivoted on a journal 10, fastened between the side plates 11. In the part 25 there is a slot 12 in which the journal 13 rests on which is pivoted one end of a connecting arm 14, whose other end is by a journal 27 connected with a knee-joint mechanism consisting of two links 17 and 18. The links are connected with each other by means of the journal 27 and a releasing arm 20, connected with the link 18 by means of a journal 29. The journal 13 is held in its position by the two shanks of a shear spring 15 (Fig. 1) which is placed around the journal 10 and whose shanks rest against a pillar 16 fastened to the rocker arm member 25. A spring 19, placed around the journal iii and resting against the journal 13, tends to turn the rocker arm in the direction of the arrow 9. If the switch is the 011 position (Fig. 4) the last-mentioned turning tendency will result in that the left shank of the shear spring 15 pushes the journal 13 with the connecting arm 14 and the journal 27 to the right, which results in a pull in the links 17 and 18. As a result, the free end of the link 17 tends, through the journal 39, to turn the contact arm 6, journalled in the tabs 23, against a fixed shoe 19 and the free end of the link 18 tends-by action of the journal 29 which is journalled in the releasing arm 20 and which in this position rests against the upper edge of a slot 23, arranged in the link 18to turn the releasing arm 21) counter-clockwise around the journal 24, on which it is journalled in the side plate, so that the free end 21 of this arm rests against the gable piece 22. Hereby the components of the switch have the position shown in Fig. 4 and the connection between the contacts 6a and b and the fixed contacts 5 and 7 is broken. The arm 6 may have only one switching-01f point 6a, 7 and the contact members 611 and 5 can be omitted. When the switch is operated in the on position, the parts should be changed from the position shown in Fig. 4 to the position shown in Fig. 2. The spring 17 is hereby tensioned and the connecting arm 14 with the journal 27 and the links 17, 18 are moved toward the left through the pressure which is exercised by the right shank of the shear spring 15 against the journal 13. A coil spring 30 whose free ends rest against the journals 27, 29 tends to press the journals in the direction away from each other. When the journal 27, influenced by the connecting arm 14, is moved toward the left (in Fig. 4), the knee, formed by the links 17 and 18, will be straightened out whereby the link 17 turns the connecting arm 6 around its bearing 23 at the right end of the arm, so that its left contact 6a moves towards the fixed contact '7, and the pull from the link 18 upon the journal 29 ceases. As a result, the spring 34 (see also Fig. 1), which has its one end pressed against the L-plate 22 and its other end extended through a hole 62a in the releasing arm 21), can turn the connecting arm 20 clockwise until the free end 21 of the arm 21) strikes against a shoe 51 on a blocking arm 36 (Figs. 1, 5 and 13).

As mentioned above, the link 18 is made with two equal link halves which are parallel with each other, each being provided with a tab 31 (Figs. 1, 3 and 8), which projects at right angles to the side plate 11 and is extended through a slot 70 in the side plate (Fig. 8). The lower edge 32 of the slot 70 forms a guiding surface for the tab 31, said guiding surface being pro- 3 vided with a notch 38. For the sake of simplicity only the edge 32 and the notch 38 of the slot 70 are shown in Figs. 1, 2, 4, 9 and 10. When the link 18 moves horizontally the tab 31 slides against the guiding surface and when the tab reaches the notch 38 it can drop down into the same which permits a displacement of the link 18 in a downwardly direction, which will be further described in the following. When the switch is in the off position the tabs 31 occupy the position shown in Fig. 4 and the position shown by dotted lines 31a in Fig. 1 and, when switching on, each 31 moves down and strikes against the guiding surface 32. and slides thereafter along the horizontal edge of the guiding surface. During the lastmentioned motion the left end 6a of the contact arm 6 takes a position between the shoe 19 and the fixed contact '7. At the same time the spring 3t) is tensioned and the arm 13 with the slot 28 is moved upwards relative to the journal 29. The pull force in the arm 14 which is necessary to tension the Spring 30 and to overcome the friction between the tabs 31 and the guiding surface 32, when the rocker arm 8, 25 has been turned clockwise during the motion loads the shear spring 15 until the journal 13 rests against the right edge of the slot 12. Close to the final position of the rocker arm the tab 31 has been brought forward to the corner 37 on the guiding surface 32 (Fig. 1A) and by the action of the shear spring 15 which presses against the journal 13 and brings this back to its rest position in the middle of the slot 12 between the shanks of the shear spring 15, when the friction between the tabs 31 and the guiding surface 32 decreases-the tab 31 is drawn over the corner (Fig. 13), after which the tab 31 on account of the pressure from the spring 30 is quickly brought down into the notch 38 of the guiding slot. As a result, the Contact arm 6 is quickly moved down against the contact members and 7 through which a momentary closing of the current circuit is obtained. The required contact pressure is obtained by the pressure from the spring 30, whose whole pressure is taken up, partly by the journal 29 and partly-by means of the journal 27 and the arm 17-by the contact arm 6. The two halves of the link 18 (Figs. 3 and 14) are kept together by a middle piece 18c and that part of the releasing arm 20, which is located between the journals 24 and 29, also consists of two plate members, connected with each other, and kept together by a middle piece 43. Also the link 17 consists of two equal pieces which are parallel to each other (Fig. 3) suitably of insulating material in order to insulate the contact arm from the mechanism. From Figs. 1 and 14 it is clear that close to the middle piece 180 on the link 18 a bent leaf spring is fastened, e. g. by a rivet 75. The upper end 44a of the spring projects slightly over the middle piece 18c and co-operates with the middle piece 43 on the arm 2% in such a way that when the switch is in the on position (Fig. 1) the upper edge of the end 44a is only a relatively short distance from the lower edge of the middle member 43, whereby the links 17 and 18, when the switch is subjected to jars, cannot move any appreciable distance in their lengthwise direction (upwards in Fig. 1). The leaf spring 44 has at the top a tab 44b (Figs. 1 and 14) which prevents the spring end 44a from sliding in to the right of the middle piece 43 which sliding would otherwise neutralize the blocking function of the spring 44. In the embodiment shown it is intended that there shall be a play of e. g. 0.2 millimetre between the upper edge of the spring end 44a and the middle piece 43 when the switch is on, which implies that the links 17 and 18 can only move 0.2 millimetre in the lengthwise direction. This prevents release of the switch releases due to jars since to cause a release due to jars the link 18 must move upwards (in Fig. 1) so much that each of the tabs 31, which are carried by the same, is moved out of the notch 38. From the drawing (Fig. 14b) it is clear that the spring 4-4 is firmly fastened to the middle piece in such a way that there is left a space a between the spring and the inner surface of the middle piece into rhich the spring can be bent when it presses against the middle piece. This means that when the link system is moved from the released to the closed position (Fig. 1A) and each of the tabs 31 during their motion in the slot 32 is at the edge 37 of the notch 38, the spring end 44 strikes aw inst the corner of the middle piece 43 and is bent against the middle piece 180, the tabs sink down into the notch 38, and the middle piece 18c of link 18 slips over the edge of the middle piece 43 to take the position shown in Fig. 1.

On the other hand, when the switch releases, the link is turned relative to the arm 20 and the spring 44 is thereby moved into such a position that it cannot block the link 18 (see Fig. 4).

The spring 44 now described does, in combination with a spring 41 in the contact arm 6 (see Figs. 1, 2 and 3), also prevent that the contact between the contact members 6a, 7 and 6b, 5 respectively is momentarily broken by jars, that is blinkings are prevented. Said spring 41, which consists of a leaf spring, is placed in the bottom of the arm 6 which is U-shaped in section and provided with a cavity on the middle, in such a way that the ends of the spring rest against the bottom of the arm 6, but the center section is at a certain distance from same bottom. The journal 39 (Fig. 1), which is journalled in the link 17, passes through an oval-shaped hole 40 in the arm 6. When the contact between the arm 6 and the contact 7 is broken, as shown in Fig. 1A, the spring 41 presses the journal 39 against the upper edge of the hole 40, but when the switch is on (Fig. l) the link 17 will, on account of the spring pressure from the spring 30, be pressed downwards, whereby the journal 39 is pressed down against the lower edge of the hole 40 by which the spring 41 is tensioned and the arm 6 is pressed against the contact 7. Even in the closed position (Fig. 1) there is a certain space 5 between the lower surface of the spring 41 and the bottom of the contact arm 6 and the spring 41 tends to press the journal 39 upwards. As mentioned above, the spring 44 on the link 18 allows a displacement of the links 1'7 and 18 due to jars through a distance of about 0.2 millimetre in their lengthwise directions. The play in the hole 40 (Fig. 1) for the journal 39 is greater than 0.2 millimetre and a motion of about 0.2 millimetre in the lengthwise direction of the links 17 and 18 will not cause the journal 39 to strike against the upper edge of the slot 40 and will therefore not cause lifting of the contact arm 6 from the fixed contacts 5 and 7. The arm 6 will instead be held by the leaf spring 41 pressed against the contacts 5 and 7 provided that the jars are not strong enough to overcome the resistance of the leaf spring 41 to the accelerating forces from the contact arm 6. The weight of the latter should therefore be kept low in relation to the pressure exercised by the leaf spring. The protection against momentary interruptions (blinkings) in the current circuit caused by blows and jars is thus materially increased.

In Fig. 113 it is assumed that the system is subjected to an accelerating force in an upwardly direction. The links 17, 18 with the tabs 31 have been displaced upwards and the leaf spring 44 has struck against the shoe surface 43a of the middle piece. The journal 39 has been brought up into the slot 40 and the pressure from the leaf spring 41, which has relaxed somewhat, is sufficient to press the arm 6 against the fixed contacts 5 and 7.

The leaf spring 41 can possibly be replaced by a coil spring 4112, e. g. a piano wire wound around the journal 39 and with its ends resting against the bottom of the arm 6, as shown in Fig. 9.

For a manual releasing of the switch the. parts, shown in Figs.:;1 and 2.sho,uld be-changedto the position: shown in Fig.4 and the rocker arm 8 is thereby turnedcounterclockwiseaarounddthe. journalzllh During the turning the slot 12 will be displaced over the journal 13 and in final: position the'journal wilLbe in .the-lefthalf of the slot 12.. spring-.15 has been .tensioned and tends to move the journal :13 and the arm 14 (which: carriesthe journal.13)-

to the right. The arm 14 is mechanically connected with the'links' 17,18.:through.pthe. journal 27 and aslong as.

At. the same time. therrleftrshank. of the shear the tabs 31 are in their notches 38 the'pressure from the arm 14 cannot break the knee formed by the links 17,.

18 which is the condition for releasing thexswitch. To enablethis there'is an operating arm 46-journalled around a pin 45 in the rocker arm- 8, 25, the configuration of said arm 46 being evident from Figs. 1 and and which co-operates with: the shoe 51-on the abovementioned blocking arm 36, the latter one being pivoted around the pin 55,-fastened to the bottom .plate' 11. A spring 52 is wound around: thepin .55 andits one-shank presses against. a pillar 54 in the bottom plate 11 and its other shank is at its end-52a perpendicularly bent and presses against the upwardly directed part; 36a of the blocking. arm 36 bywhich this latter-:is given .a counter-clockwise turning. moment. The motion is limited by a firmstop' member 56. The above-mentioned operating arm 46 is in its free end formed into a hook 50-and is on its lower part formed into a cam 48 which, :when the arm 46 is displaced by the movements ofthe rocker arm 18, 25,

slides against-a pillar 49 fastenedato the bottom. plate,

by which the hook S0 is brought upwards or downwards. The cam 48 on the-operating arm 46'is. kept pressed against the pillar 49-through the-spring 47 placed around thefirm pillar 54- When the arm46, on releasing the switch through influence by the rocker arm 8, is moved to the left (Fig. l) the hook-50 strikes against the shoe 51 (seealso Fig. 5) and drives-thisshoe so that the blocking arm .36 is turned counter-clockwise against the action of the'spring 52. As mentioned before, the end 21 of the releasing arm 20 is under spring pressure partly from the spring 30, which presses against the pin 29, journalled in the-arm 2l,'-thereby-giving the: arm 20 a clockwise'turning moment, and against the-shoe51 and when this latter'one is by the hook 50 moved clear of the end 21 so-that this does not get any support by the shoe 51, the releasing arm 20 willturn clockwise, whereby the knee, formed by the arm 20 and thelink 18,.is bent to the left at a some what-smaller angle than in Fig.- 4. The pin 29,- which is journalled in the releasing arm 20, is moved against the upper edge of the slot 28 through the. pressure from the spring 30 and during the continued motion, when the spring 34 alone turns the arm 20 clockwise, the pin 29.will carry with it the link 18 whereby the: tabs 31 are pulled up from their notches 38." At this moment, when the parts of themechanism take the position shown in Fig. la, the pressure from the-arm 14 can be released.

and the pin 27 with the links 17iand18. be rapidly carried to the right, whereby the link 17 pulls up the contact'arm 6 so that switching-oil" is effected and the. link 18-by having the upper edge .ofthe slot, 28 resting against thepin '29pulls the pin 29 downwards to the left,..giving it a counter-clockwise turning moment which is greater than and counter-to the moment from .the spring 30 on the arm 20, so that the end of said arm, previouslyuturned downwards, is carried upwards until it strikes; against the L piece 22 of the bottom plate. All @components of'the switch have then been changed to the positions. shown in Fig. 4. The hook 50 of the operating arm 46 -has thereby been carried upwardthrough vco-operation between the cam 48 and the pillar 49-whereby-.the blockingarm 36 with the shoe 51 operated by thespring turningmotion to the position shown in-Fig. 1.

partly from the spring 34 52- can be returned by a clockwise The releasing of the switch can also be made thermally. For this' purpose there is a bimetallic spring 2 (Fig. 4a), mounted on the terminals 1 and 5, through which spring the current passes and which is heated by the current. 011 the blocking arm 36 there is by the rivet 74 fastened a band-shaped arm 70 whose end is formed into a bushing 71, in which a screw 72 is threaded which carries a ball 53 of insulating material. The distance between the ball 53 and the bimetallic spring 2 can be adjusted by means of the screw 72. If it is assumed that the switch is on and the current exceeds a previously determined value, and that the blocking arm 36through influence by the bimetallic spring 2 which by the heating has turned to the right-has turned counter-clockwise so much that the shoe 51 on the blocking arm has been carried away from the end 21 by which the releasing arm 20 rests against the shoe 51, the-arm 20 can be turned clockwise. As a result the parts are returned in the abovementioned manner to the position shown in Fig. 4 under the influence of the spring 19 in the rocker arm which spring, when the switch is off (Fig. 1), tends to carry the arm 14 and therewith the knee between the links 17 and 18 to the right.

In the case that the rocker arm 3, after switching on, is retained in its position (as indicated in Fig. 10) and a switching ofi", caused in a thermal way occurs, the releasing arm 20 under the influence of the spring 34 is turned a greater angle than at a normal release. The pin 29 in one end of the releasing arm 26 will thereby bring with it the links 17 and 18-and also the contact arm 6 upwards, whereby the contact between the arm and the fixed contact 7 even in this case is broken.

In the event it is desired that the switch is released thermally but not manually it is only necessary to remove the operating arm 46 which by means of its hook 50 operates the blocking arm 36. The switch may then be manually switched on but releasing is only possible by a thermal action.

The one-pole switch now described is used as a component in a multiple-pole switch.

In Figs. 11 and 12 is shown a three-pole switch comprising three single-pole switches A, B and C, whereby only the middle switch has been provided with a handle 8. When switching on manually the handle 8 on the rocker arm of the switch B is operated and to cause also the switches A and C to be switched on, the rocker arm of the switch B is provided with driving members which at the motion of the rocker arm in switch B carry with them the rocker arms in the switches A and C. The lower part of each rocker arm consists, as mentioned before, of two plate pieces 25 which are parallel to each other as shown in Fig. 12, which is a section along the line H-H in Fig. 2. Each plate piece 25 of the switch B is now provided with a tab 57 which is bent up perpendicular to the plate (see Fig. 1 and Fig. 12). The plate piece 25 on each side switch A and C respectively, which is located close to the switch B, is also provided with a tab 56 (Figs. 1c and 12), so placed that when the rocker arm in the middle switch B is turned when switching in, the rocker arms in the switches A and C are carried along so that these switches also are switched in. The tabs 56 and 57 project out of the sides of the side plates 11 and 11a through openings 73 made in the same (see Fig. 8).

When switching ofr"manually or thermally-one of the switches, the motion-transmission for the adjacent switch must be made via the blocking arm 36, as this arm controls the releasing of the switch. For this purpose the blocking arms 36 in the various switches A, B, C are connected together with one another by connecting arms 58 (see Fig. 11, details in Fig. 11a) which are perpendicularly bent out in the ends. Each blocking arm 36 is provided with two slots 60 (see Figs. 1, 11, 13A and C). The connecting arm 58 is riveted with the rivet 59 (see Fig. 11) to the blocking arm 36 of the switch A and has its left end inserted in the left slot 60 in the same blocking arm. The right end of the arm 58 is inserted in the left slot 60 in the blocking arm 36 of the switch B. A connecting arm 58a is in the same manner fastened to the blocking arm 36 of the switch C as indicated in Fig. 11. The right (resp. left) end of the connecting arm 58 (resp. 58a) is consequently inserted into its corresponding slot 60 in the blocking arm 36 of the middle switch B, whereby there is a certain space 61 (Fig. 11) between the connecting arm 58 (resp. 58a) and the upper (resp. lower) edge of the slot 60, whereby one blocking arm 36 of the switches A, B or C respectively can turn a certain angle without the connecting arm 58 and 58a respectively touching any of the sides in the corresponding slot 60, that is without the arm 58, 58a driving the blocking arm 36 of the adjacent switch. The force obtained from the bimetal 2 on thermal releasing is not suificient to turn all three blocking arms in the switches A, B and C, and the device has therefore been so designed that a certain additional motion is obtained when one of the switches has started to release, which additional motion causes that also the two other switches release. On the releasing arm 20 in each switch there is provided for this purpose a downwardly directed projection part 62, which can strike against a pin 63 on the blocking arm 36 (Figs. 1, 2 and 5 If the switch from a closed position (Fig. 2) starts to release owing to that the bimetal 2 bends and acts upon the insulating ball 53, the blocking arm 36 is turned in the manner previously indicated, so that the releasing arm is made free and turns clockwise, whereby the projection part 62 strikes against the pin 63 on the blocking arm 36. The clockwise turning moment of the releasing arm 20 is effected by the springs 30, 34 and 41 whereby the blocking arm 36 receives an essential contribution to the counter-clockwise turning motion that is given the arm on account of influence from the bimetal 2. This action is sufiicient for the blocking arm 36 of the switch that has released, e. g. the middle switch B, to turnby means of the connecting arms 53 and 58aand thereby drive the blocking arms 36 of the switches A and C. The space 61 between the connecting arm 58 and the inner edge of the slot 6i) should be so dimensioned that the end of the arm 58 does not make contact with the edge of the slot before the projection part 62 on the releasing arm 20 by striking against the pin 63 on the blocking arm 36 has imparted to the blocking arm a small additional motion. In the case that one of the switches A or C, e. g. A, releases first, the blocking arm of this switch will through the arm 58 carry with it the blocking arm in the switch B, so that also this switch releases. Through the additional moment which is obtained in the last mentioned switch through co-operation between the projection part 62 and the pin 63 in the last mentioned switch, the connecting arm 58a can carry with it the blocking arm 36 in the switch C by which all three switches will be released. In the case that by two-pole switching only two switches are used, only one connecting arm will of course be required. The above-mentioned additional motion of the blocking arm 36, which is effected through co-operation between the projection part 62 on the arm 26 and the pin 63 on the blocking arm 36 ceases after the tip of the projection part 62 has turned the blocking arm to such a position that the right edge 64 of the projection part 62 slides against the surface of the pin 65. To this end, the last-mentioned edge is formed as a part of a circle, whose centre is the centre of the journal 24 (see Fig. l).

The now described additional motion of the blocking arm 36 has been described in connection with thermal releasing, but this motion will also take place at manual releasing of the switch, whereby it may be assumed that the handle 8 of the three-pole switch shown in Fig. 11 is operated. The hook 50 on the arm 46 carries thereby with it as described above, the shoe Sll on the blocking arm 36 when the handle 8 on manual releasing is turned counter-clockwise. However, at the same time the arm 46 with the shoe is lifted (Fig. l), on account of cooperation between the cam 48 on the arm 46 and the pillar 49, and when the hook 50 has turned the blocking arm 36 with the shoe 51 to such a position that the end 21 of the releasing arm 20 is clear of the shoe 51, so that the arm 20 can release, the hook 50 has been raised so much that, on the continued motion to the left of the arm 46, it can no longer carry with it the shoe 51. At this moment the tab 62 on the releasing arm 20 strikes against the pin 63 on the blocking arm 36, for which reason even in this case an additional motion for the blocking arm 36 is obtained which is sufficient to turn the blocking arm of the adjacent switch.

This affords the further advantage that manual releasing of the switch will not permit the switch to be operated in such a way that only one of the poles releases while the others remain in closed position. This would be possible-if there was no device for additional motionby turning the rocker arm of that switch which is provided with said arm, only so much that releasing of this switch is barely obtained and to keep the rocker arm thereafter in this position. A releasing of the other poles would not then take place before the rocker arm is freed. On the other hand, in the switch according to the invention, all

poles are simultaneouly released also by manual operation.

The device now described-by means of which an additional motion is given to the blocking arm 36 when the releasing arm 20 is turned and which device is the object of the present application-4s of course independent of how the switch-unit, from which the multi-switch has been combined, has been designed in detail. The device of giving additional motion can be applied to every switchunit which comprises a knee-joint mechanism and one with the same co-operating releasing arm and a blocking arm controlling said releasing arm which blocking arm can be operated by a heat sensitive member. Thus it is not necessary that the switch is provided with any device to prevent blinkings due to jars, for which reason e. g. the leaf spring 44, fastened to the link 18 and/or the spring 41 in the arm 6, can be omitted.

The band-shaped arm 70, which carries the insulating ball 53 and which is carried by the blocking arm 36, can

consist of a bimetallic strip, by which temperature compensation is obtained for temperature variations in the ambient air. If e. g. the temperature of the ambient air increases, it is assumed that the bimetallic strip 2 bends to the right, for which reason the distance between the strip 2 and the ballin the case that the arm is made of ordinary metal-decreases without any current passing the bimetal. When the bimetal 2 is then heated by the current, it will make contact with the insulating ball 53 and release the switch at a lower current than the one required before the temperature of the ambient air increased. To compensate this error the arm 70 is made of bimetal so arranged, that when the air temperature increases, the arm 70 also bends to the right, by which the distance between the bimetal 2 and the ball 53 will be the same as before the heating.

1 claim:

1. A multi-pole overload tripping switch comprising, in combination, a plurality of switch units disposed adjacent to each other in juxtaposed relationship, each of said units comprising a single pole tripping switch having a kneejoint operating mechanism including a first link and a second link pivotally connected adjacent one end of each said links, the opposite end of said first link connected to a movable contact member, at least one fixed contact member, said movable contact member being selectively engageable with at least one fixed contact member, a releasing arm rotatably supported in the unit, the opposite end of said second link being pivotally connected to said releasing arm, a blocking arm pivotally supported in said unit normally blocking the movement of said releasing arm, spring means associated with said releasing arm tending to rotate said releasing arm into bearing engagement with said blocking arm, temperature responsive means associated with said blocking arm for initially rotating said blocking arm out of blocking engagement with said releasing arm thereby efiiecting rotational movement thereof under action of said spring means, said rotational movement of said releasing arm being operative to rotate said releasing arm into further engagement with said blocking arm to effect additional rotation of said blocking arm under the action of said spring means, lost motion means connecting the blocking arms of adjacent switch units, said lost motion means permitting the initial rotation of one of said blocking arms independently of an adjacent blocking arm and being operative to transmit said additional rotational movement thereof to said adjacent blocking arm to rotate said adjacent blocking arm out of blocking relationship with the associated releasing arm to effect release thereof.

2. A multi-pole overload tripping switch as set forth in claim 1, wherein tab means are disposed on said releasing arm for engaging a shoulder disposed on said blocking arm during rotation of said releasing arm to efiect said additional rotation of said blocking arm.

3. A multi-pole overload tripping switch as set forth in claim 1, wherein said switch units are arranged with the axes of rotation of the blocking arms of each unit coinciding with each other, said lost motion means comprising a connecting arm secured at one end to the blocking arm 10 of one said unit with the other end thereof in spaced relationship to the blocking arm of an adjacent unit, the initial rotation of said one blocking arm to a releasing position being operative to move said connecting arm into motion transmitting engagement with said blocking arm of said adjacent unit.

4. A multi-pole overload tripping switch as set forth in claim 2, wherein said switch comprises three switch units arranged in juxtaposed relationship with one of said switch units being disposed between two outside switch units, a connecting arm secured at one end to the blocking arm of each said outside switch units, the opposite end of each connecting arm being operatively engaged with the blocking arm of said switch unit disposed between said outside switch units.

References Cited in the file of this patent UNITED STATES PATENTS 2,015,633 Dorfman Sept. 24, 1935 2,065,357 Von Hoorn Dec. 22, 1936 2,091,941 Frank Aug. 31, 1937 2,170,412 Jennings Aug. 22, 1939 2,623,967 Herman et al Dec. 30, 1952 2,653,202 Cole Sept. 22, 1953 2,666,828 Dyer et a1 Ian. 19, 1954 FOREIGN PATENTS 49,051 France Jan. 19, 1954

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