US2816986A - Overload tripping switch - Google Patents

Description

E. J. HAGDAHL OVERLOAD TR'IPPING SWITCH Dec. 17, 1957 8 Sheets-Sheet 1 Filed Deo. 22. 1954 Dec. 17, 1957 E. J. HAGDAHL OVERLOAD TRIPPING SWITCH 8 Sheets-Sheet 2 Filed DeG. 22. 1954 L y MJ @E wim Mg M M f Dec. 17, 1957 E. J. HAGDAHL OVERLOAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 5 Dec. 17, 1957 E, J, HAGDAHL 2,816,986

OVERLOAD TRIPPING SWITCH Filed DBG. 22. 1954 8 Sheets-Sheet 4 IN VEA/rw? ERA/Jv' fof/9N Hasn/wa 5f mi@ Dec. 17, 1957 E. J. HAGDAHL ovERLoAD TRIPPING SWITCH 8 Sheets-Sheet 5 Filed Dec. 22. 1954 3f @mi Hw /Qrro RNE r Dec. 17, 1957 E. J. HAGDAHL 2,816,986

ovERLoAD TRIPPING SWITCH Filed Dec. 22. 1954 8 Sheets-Sheet 6.

/Qrromvfr Dec. 17, 1957 E. J. HAGDAHL ovERLoAD TRIPPING SWITCH 8 Sheets-Sheet 7 Filed Dec. 22. 1954 rro mvfr Dec. 17, 1957 E. J. HAGDAHL 2,815,986

OVERLOAD TRIPPING SWITCH Filed Dec. 22, 1954 8 Sheets-Sheet 8 ArfoR/vfr United States Patent O ovERLoAD TRrPPlNG SWITCH Johan Hagdahl, Bromma, Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a corporation of Sweden Application December 22, 1954, Serial No. 476,954 Claims priority, application Sweden December 23, 1953 Claims. (Cl. 200-116) The invention relates to an overload tripping switch of the type in which the operating system comprises a knee-joint 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. Such switches have the disadvantage that the switch, if it is in on position, opens due to jars or causes momentary interruptions in the circui-t that the switch controls. Switches of this type which are known up to now have also a complicated design. The present invention intends to provide a switch of this type, in which the now mentioned disadvantages have been eliminated.

The invention will be further described with reference to the attached drawings which show a number 4of ernbodiments.

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

Figs. 2, 4 and 10 correspond to Fig. 1 but are made on a reduced scale in which case the parts, however, shown in Figs. 4 and 10 are shown in the position they have when the switch is in o position. Fig. 4a is a section taken along the line E--E in Fig. 4. Figs. 3, 5, 6 and 7 are sections taken along the lines A-A, F-F, G-G 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 iixed 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 H-H 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. 14 A and B show a link viewed from the front and the side respectively.

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

Figs. 16-19 show a modication whereby Figs. 16-18 show, viewed from the side in ydiiferent positions, the parts of the mechanism according to Fig. 1 which are affected by the modification. Fig. 19 shows a section taken along the line I--I in Fig. 16.

All components of the switch are mounted between two side plates 11 and 11a, of which 11 in one edge is bent to form an L-member 22. The turnable parts of the switch are carried by journals with bearings in the two side plates 11 and 11a. In Fig. l is shown the position of the various components when the switch is in on position. The circuit for the current that is to be switched oi is connected to the terminals 1 and 7 and the current passes from the terminal 1 through a bimetal 2 and the CFI ICC

terminal 5 and through the contact arm 6 operated by the switch 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 4a plate 71 of insulating material arranged on the inside of each side plate 11 and 11a respectively. Said slot 72 (Fig. l) has a sloping edge at the top whereby the arm 6 is allowed to take the position shown by lines `of dots and dashes in Fig. 1. The arm 6 is in 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 consist of a rocker arm 8, 25, whereby 8 is the handle and 25 the lower part of the arm comprising 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 connected by a journal 27 with a knee-joint mechanism. This mechanism comprises two links 17 and 18 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 lof a shear spring 15 (Fig. l) 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 10 and resting against the journal 13, tends to turn the rocker arm in the direction ot the arrow 9. If the switch is in the off position (Fig. 4) the last mentioned turning tendency will result in that the left shank of the shear spring 1S pushes the journal 13 with the connecting arm 14 and the journal 27 to the right, which results in a pull in the links 11 and 18. Thereby the free end of the link 17 tends, via the journal 39, to turn the contact arm 6, journalled in the tabs 23, against a xed shoe 19 and the free end ot' the link 18 tends-by action of the journal 29 which is journalled in the releasing arm 2t) and which in this position rests against the upper edge of a slot 28, arranged in the link 18--to turn the releasing arm 20 counter-clockwise around the journal 24, on which it is journalled in the side plate, so that the tree end 21 of this arm rests against the gable piece 22. Hereby the components or' the switch have the position shown in Fig. 4 and the connection between the contacts 6a and b and the xed contacts 5 and 7 is broken. The arm 6 may have only one switching- ott point 6a, 7 and the contact members 6b and 5 may 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 and the handle 8 is thereby turned clockwise (Fig. 4). The spring 19 is hereby tensioned and the connecting arm 14 with the journal 27 and the links 17, 18 is brought to 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, inuenced by the .connecting arm 14, is moved to the left (in Fig. 4), the knee, formed by the links 17 and 18, will be straightened out which involves, partly that 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 partly tha-t the pull from the link 18 upon the journal 29 ceases, through which `the spring 34 (see also Fig. l), which has its one end pressed against the L arm 22 and its other end brought through a hole 62a in the releasing arm 20, can turn the connecting arm 20 clockwise until the free end 21 of the arm 20 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 andY 8), which projects at right angles to the side plate 11, and is brought 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 provided with a notch 38. For the sake of simplicity only the edge 32 and the notch 38 of the slot 78 have been drawn in Figs. 1, 2, 4, 9 and 10. When the link 18 moves horizontally the tab 31 slides against the guiding surface andv 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, inthe following. When the switch isV inthe of position the tabs 31 hasthe position shown in Fig. 4 and. thevposition shown by dotted lines 31a in Fig. 1 and, when switching on, each tab 31 moves down and strikes against the guidf ing surface 32 and slides thereafter along the horizontal edge of the guiding surface. Duringthe lastmentioned motion the left end 6a of the contact arm 6`takes aposition between the shoe 19 and the Xed contact 7. At the same time the spring 30 is ltensioned and theA arnrlS with the slot 28 is brought 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, has been turned clockwise during the motionloads 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 thecorner 37 on the action of guiding surface 32 (Fig, 1A) and by the shear spring 15-which presses against the journal 13 and brings this back to itsv rest position in the middle of the slot 12 between the shanks of the .shear spring 15, when the friction betweenthe tabs 31n andthe guiding surface 32 decreases-the tab 31 is drawn over the corner (Fig. 1B), after which the tab 31 on account of the pressure from the spring is quickly brought down into the notch 38 of the guiding slot. As a result, the contact arm 6 is quickly brought down against ythecontact members 5 and 7 through which a momentary closing of the current circuit is obtained. Necessary Contact pressure is obtained by the pressure from the spring 30,A

whose whole pressure is taken up, partly by the journal 29 andpartly--by means of the journal27 and the Varm. 17-by the contact arm 6. The two halves of ,theglink 18 (Figs). 3 and 14) are kept together by a middle'piece 18a and that part of the releasing arm Ztl, which is located between the journals 24 and 29, also consists of two plate members, connected with each other, and kept together by avmiddle 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 armfrom the mechanism. FromFigs. 1 and 14 it isclear that near the/middle piece 18e on the link' 18 is bent and fastened, e. g. by'a rivet 7S, aleaf spring 44 whose upper end.44a.projects slightly over themiddle piece 18e and co-operates with the middle piece-43 on the arm Ztl `in such a way that when the switch is in on position (Fig. 1) the upper edge of the-end 44a is only a relatively short distancel from the lower edge of the iniddle member 43, through which it is prevented that the links 17 and 18, when theswitch is subjected to jars, move any appreciable distancein their lengthwise direction (upwards in Fig.l l). The leaf spring-44 has at the top Va tab 44h (Figs.,1 and 14) which prevents the spring metre between the upper edge of the springend 44a andA t the middle piece 43 when the switch is 011, which implies that the links 17 and 18 can only move 0.2 millimetreV in the lengthwise direction. Thereby it is prevented that the switch releases for shakes since it is required for making a releasing by a jar possible, that the link 18 moves upwards (in Fig. 1) so much that each of the tabs 31, which is carried by the same, is moved out of the notch 38. From the drawing (Fig. l4b) it is clear that the spring 44 is rmly fastened` to the middle piece 18C in` such a way that there is a certain space a between the spring and the inner surface of the middle piece through which the spring can be bent when it presses against the middle piece. This means that when the link system is transferred from released to closed position (Fig. 1A) and cach 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 against the corner of the middle piece 43 and is bent against the middle piece 18o in order then, when the tabs sink down into the notch 38, to slip over the edge of the middle piece 43 and take the position shown in Fig. 1.

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

The spring 44 now described, in combinationwith a spring 41 in the contact arm 6 (see Figs. 1, 2 and 3), also prevents that the contact between the contact members 6a, 7 and 6b, S 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. l), whichis 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. 1) thelink 17 will, on account of the springl 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 closed position (Fig. 1) there is a certain space 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. above, thespring 44 on the link 18` allowed that the links 17 and 18 could be displaced by jars about 0.2 millimetre in their lengthwise directions. The playin 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 jour, nal 39 to strike against the upper edge;of the -slot 40 and will therefore not involve that the contact arm 6 is lifted, from the fixed contacts 5 and 7. The arm.6.will insteadA 17, 18 with the tabs 31 have been displacedupwards and the leaf spring 44 has struck against the `shoe surface 43a of the middle piece. The journal*l 39 has beenbrought up into the slot 40andthe pressure from theleaf spring,i 41, which has relaxed somewhat, is suicient vto press ,theV

arm 6 against the fixed contacts 5 and 7.

The leaf spring 41 may be replaced by a coil spring As mentioned.

41h, e. g. a piano wire wound around the journal 39 and withits ends resting againstthe bottomof the arm 6, as shown in Fig. 9.

For a manual releasing of the switch the parts shown in Figs. 1 and 2 should be changed to the position shown in Fig. 4 and the rocker arm 8 is thereby turned counterclockwise around the journal 10. During the turning the slot 12 will be displaced over the journal 13 and in linal position the journal will be in the left half of the slot 12. At the same time the left shank of the shear spring 15 has been loaded and ltends to move the journal 13 and the arm 14 (which carries thejournal 13) to the right. The arm 14 is mechanically connected with the links 17, 18 through the journal 27 and as long as the tabs 31 are in their notches 38 the pressure from the arm 14 cannot overcome the knee formed by the links 17, 18 which is the condition for releasing the switch. To enable this there is an operating arm 46 journalled around a pin 45 in the rocker arm 8, 25, the appearance of said arm 46 being evident from Figs. 1 and 15 and which co-operates with the shoe 51 on the above-mentioned blocking arm 36, the latter one being pivoted around the pin 55, fastened to the bottom plate 11. A spring 52 is wound around the pin 55 and its 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 by which this latter is given a counter-clockwise turning moment. The motion is limited by a rm stop member 56. The abovementioned 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 of the rocker arm 18, 25, slides against a pillar 49 fastened to the bottom plate, whereby the hook 50 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 the rm pillar 54. When the arm 46, on releasing the switch by the rocker arm 8, is moved to the left (Fig. 1) the hook 50 strikes against the shoe 51 (see also Fig. 5) and drives this 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 rests under spring pressure partly from the spring 30, which presses against the pin 29, journalled in the arm 20, thereby giving the arm 20 a clockwise turning moment, and partly from the spring 34 against the shoe 51 and when this latter one is by the hook 50 moved clear of the end 21 so that this end is no longer restrained by the shoe 51, the releasing arm 20 will turn clockwise, whereby the knee, formed by the arm 20 and the link 18, is bent to the left at a somewhat smaller angle than in Fig. 4. The pin 29, which is journalled in the releasing arm 20, is brought up 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 the mechanism take the position shown in Fig. lc, the pressure from the arm 14 lcan be released and the pin 27 with the links 17 and 18 be rapidly carried to the right, whereby the link 17 pulls up the contact arm 6 so that switching-olf is made and the link 18-by having the upper edge of the slot 28 resting against the pin 29--pulls the pin 29 downwards to the right, giving 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, previously. turned downwards, is carried upwards until it strikes against the L-member 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-through co-operation between the ca m 48 and the pillar 49--been carried upwards to enable that the'blocking arm v3.6 with the shoe 51 operated `by 6.. the spring 52 through a clockwise turning motion can be brought back to the position shown in Fig. 1.

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. On 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, it is assumed that the blocking arm 36-through inuence 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 and the arm 20 can therefore be` turned clockwise and the parts thereby be 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 ott (Fig. l), 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 8, after switching on, is retained in its position (as indicated in Fig. l0) and a switching off, caused in a thermal way occurs, the releasing arm 20 is under the influence of the spring 34 turned a greater angle than at a normal release. The pin 29 in one end of the releasing arm 20 will thereby bring with it the links 17 and 18 and also the contact arm 6 upwards, by which the contact between the arm 6 and the fixed contact 7 even in this case is broken.

A single-pole switch has been described above. In the case that a multi-pole switch is used, e. g. in three sections, it is desirable that all sections are released even if only one of the sections is overloaded. This requirement can be fulfilled by building together several switches according to the invention in a manner that will now be further explained.

In Figs. ll and 12 is shown a three-pole switch, built together of 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 enable thereby that also the switches A and C are switched on, 1

the rocker arm of the switch B is provided with driving members which at the motion of the rocker arm in switch B bring 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 (see Fig. l2, 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 i 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. lc and l2), 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 brought with it so that even these switches 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 off-manually or thermally-one of the switches, the motion-transmission to 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. 1l, 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, 1l, 13A and C).

The connecting arm 58 is riveted with the rivet 59 (see Fig:A 11) to'ithei blocking:VA arrrr36-l of 'thez-'switchgAz and 1 has its left end.insertedffinvtherleft'slotfll'inzzthe .sarnea blocking-:arma: The=right end ofztherarm1=58lis'inserted in .theleftl slot r60'fin theeblockingfarmscof the switch;

Fig. 11.: The right. (resp.l left) end; of:the.connecting.

arrrrz. 58- (resp; 58a) lis consequently insettedsiinto.- its.'v corresponding-slot 60mthe blocking 'arrrril of the middle L.

switch B; whereby there eis a1certairr-.space :611.(Figr: 11) between the'connecting arrnz.'58'l(resp;;58.) `andthe upper (resp: lower) edge :of-the. .slot:60,=.which ,enables thatuone blockingv arm 36a of .'thefswitches'aA; B or.-G.respectively,` can :.turn gazzcertainr angle-.without the :connecting i zarmfSS; andcSStz respectively touching: any of .ther-sides inx the corresponding .slot60,. thatis cwithoutzthe-arnr 5S, 58a. driving the :blocking zar-m. 36-.ofjthe1adjacent switch.; The f force .obtained .from.;the:bimetall2. on .thermal releasing.

is not .sucient i to. turn.-a1l. three @blocking arms. in.. the switches A, B and C, and the device-has therefore been f so designed that acertainfadditional. motion-is obtained when one of the switches hasstarted'tonreleaseg which additional.- motion causes thataalso the twoi other 'switches rele-ase. On. the releasingarm 20-in eachswitchthere is for this purpose a downwardly directed projection.

part 62, whichican strike against a .pinL 63 onf the blocking arm 36 (Figs. 1, 2 and 5).l If the switchfroma closed.

position-(Fig. 2) starts to releaseowing toth'at the bimetal 2 bends and acts upon the insulating ball 53, the blocking arm 36 is. turned Ain the. manner previously indicated, sothat the releasing arm 20 is madevfree and turns clockwise,.whereby` the projection part 62 strikes against the pin 63A on the blockingk arm 36. The Vclockwise turning moment of the releasing .arm 20 is effected by the springs 30, 34 and 41 and hereby theblocking arm 36 receives an essential. contribution .to the counter-clockwise turning motion .that is given the armen account of inuence from the .bimetalf2, .which contribution. issufticient .that the blocking arm 36 of the switchthat has released, e. g. the

middle switch B, shallon its .turningby meansofthe l connecting arms 58 and 58a-be able to drive the blocking arms 36 ofthe switches A and C. The space 61 between the connecting arm 58 andthe inner edge of the slot 60 vshould be so dimensioned that the end of the arm 5S does not make contact with the edge of the slot the pin 63 in the last-mentioned switch, the connecting arrn'58a'will carry with it the blocking arm 36 in the switch C whereby all three switches will be released. Inthe casethat by two-pole switching only'two'switches are used, only one connecting arm 58 will of coursebe required; The yabove-mentioned additional motion of the blocking arm 36, which is effected through co-*operation between the projection part 62 on the arm 20 and the pin 63 on the blocking arm 36 ceases'after the tip of the projection part 62 has turned the blocking arm4 to such a position that the right edge 64 of the projection part 62 slides against the surface of the pin 63. The last-mentioned edge is namely formed as a partof a circle,- wh'ose centre is the centre of the journal 24(see Fig;` l).

The-now described additional motion of the'blockingarnr36 has been described in connection with '.thermalre# leasing, but this frnotion will also take-*place at manual releasing of theswitch, whereby it may b'e-'assumed'that theihandle 8 ofthe three-polefswitch shown inFig. 1l is operated The -hookfSO` on thearm46Lcarries-=with CII it as :.described ;above,. thezshove 51.v orrithe .blocking .arm

36 .'.when the handler18.. onlrnanual.. releasingfr is turned: However, at the same .timethefarmn counter-clockwise. 46:with:,th'e.shoe 50 islifted'KFig-,f 1), on; account ofxcof operation; between. the f carnn48on` the arm 46s andzth'ei pillarv 49,-.and in the movementwhen. the 'ho0k150 hasl turned .thevblocking arm 36W/,ith the shoe 51 to sucha position; that'the end 21 of the .releasing arm. 20 .moves clearof -'the-.shoe51,' so.that` the' arm 20can release, the. hook S0'has been raised so much that, onxthecontinued.

motion to the left of the-arm 146,l it can no longer carry witlrit theshoe 51. releasing `arm'20 strikes :against-the pin'63 on; the .blockingwarrn 36,-forfwhichv reasonveven: in this case an additional. .motion -forthe bloc-kinggarm. 36v is obtainedwhich is suficient'to turn:the blocking arm ofthe adjacent switch.

The invention cantbe'modied in .several ways rwithin the scope. of the idea of. thelinvention. the link 18 may be effected, instead of 4by the leaf spring 44, by a spring actuatedblocking member 80, journalled on. the pin 29 (Figstl6.-l9). The blocking member 80 is in its oneend provided with a shoe Si, intended to cooperate with the pin..27, and in the ,other endy provided .with a..ilange 82,. against whichV cneend ,rests of a coil spring 83, wound around the pin 29, which. spring tends to. turn the,blocking.mernber tlceunter-clockwise, so that the .ilange82. rests againsty the middle piece 43. in the arm. 20. When theswitch. is,.on. (Fig. l) the parts takethe position. shownl in Figs.v 16 and19, the shoe 81 is ata slight. distance .from .the pin 27 and fadisplacement ofthe liiik'.1S.iri. its lengthwise direction is then prevented? by the, blocking.. member 80 since. this is journalledon the pin .29,whichis liked in this position of the mechanism. When the switch is. to be released the arm 20a1idfthe link 18 areturned-as described aboverelative to eachother and thewarm 20 drives the'blocking member 80`to .the position showny in Fig'. l7,`,in which the blockingarm 80 cannot prevent. the motion of'the link 18. position the. pin 29 is-just before the tabs 31 fallinto the notches 38'-in. the lower part of the slot 28' and on turningrthe link lclockwise aroundthe pin 29, the pin 27 engages theshoe Slfand turns away the blocking member 80' clockwise, against the vaction ofthe.spring 83, fromthe position this has when the spring 83 presses the flange 82"against the middle-piece 43 (aboutl the position the member 80 has in Fig. 16) vand to the position shown in Fig. 1S. Fromlthis position the tabs 31 fall down intothe notches lErin the way described above, whereby theblocking member 841" bythe spring 83 is turned counter-'clockwisetothe blocking 'position shown in Fig. 16.v As `it wouldseem; even in vthis embodiment the blocking member prevents thelink 18 to be displaced in "its lengthwise'direction 'more than a limited part when the'switch ison; withoutfthe blockingrrnember preventingthe 'motion;of"thefparts at-on and off operation of'theswitch';

The invention'can also be'modied in such a way that the bandeshaped-'arm' '70, carriedv by the blocking arm 36',l which'carries'the Vinsulatingball 53 consists of a bi# metallicstrip, whereby temperature compensation is obtained for tcmperaturevariations in theambient air. If e. g. the-temperatureV of 'theambient air increases, it is assumed thatthe bimetallic strip 2 turns to the right on account of vwhich the distance between the strip 2 and the ball has decreased-irr the f caseethat the arm 70 consists ofl ordinary metal-without-any current passing the bimetal. When the'bimetal' 2 is thenheated by the To compensatethis error the'arm70 consists of bimetal so-arranged that when the temperature 'of the air increases. alsothefarmf70 bends -toftherighn vby which thedistance.

At this moment the tab 62 on the.

The blocking of.

When the switch is to beoperated to on' 9 between the bimetal 2 and the ball 53 will be the same as before the heating.

I claim:

1. An overload tripping switch having a housing and a knee joint mechanism comprising a first link and a second link, a journal pivotally connecting one end of said first link to one end of said second link, a connecting arm having one end in engagement with said journal for effecting movement thereof, a movable contact member secured to the opposite end of said first link adapted to engage at least one fixed contact member, a releasing arm pivotally secured to said housing and being pivotally and displaceably connected at one extremity to the opposite end of said second link, a heat sensitive member controlling the pivotal movement of said releasing arm to a releasing position, blocking means comprising a spring actuated blocking member and a shoulder member, one of said members being associated with said second link and the other of said members being associated with said releasing arm, relative rotation of said releasing arm and said second link towards an engaged position of said movable contact member with said fixed contact member being operative to dispose said spring actuated blocking member in blocking longitudinal alignment with said shoulder member, said blocking means limiting relative longitudinal movement of said second link and said releasing arm towards each other when said movable contact member is in engaged position with said fixed contact member.

2. An overload tripping switch as set forth in claim 1, wherein said blocking member is secured to said second link, and said shoulder member is fastened to said releasing arm, said blocking member comprising a leaf spring having one end secured to said second link with the plane of said leaf spring at substantially right angles to the plane of said second link, the lengthwise direction of said leaf spring coinciding with the lengthwise direction of said second link.

3. An overload tripping switch as set forth in claim 2, wherein said second link and said releasing arm each comprise a pair of spaced parallel members, a middle piece connecting each pair of members intermediate their longitudinal extremities, said middle piece of said second link comprising said leaf spring, and said middle piece of said releasing arm forming said shoulder member.

4. An overload tripping switch as set forth in claim 1, wherein said movable contact means is rotatably and displaceably supported intermediate its ends by said rst link on a journal and is adapted to be displaced in a direction perpendicular to the lengthwise direction thereof, spring means disposed in said connection between said first link and said movable contact member urging said movable contact member into a direction away from said first link.

5. An overload tripping switch as set forth in claim 4, wherein said journal is carried by said first link and said spring comprises a coil spring, said coil spring encompassing said journal and having its free end in engagement with said movable contact member on each side of said journal.

6. An overload tripping switch as set forth in claim 1,

wherein the connection of said releasing arm and said second link comprises a journal, said blocking member comprising a blocking arm rotatably supported on `said journal and said shoulder member comprises said journal connecting said first link and said second link, spring means associated with said blocking arm urging said arm into engagement with said releasing arm, movement of said first link when said movable contact member is in engaged position with said fixed contact being limited by the engagement of said blocking arm with said journal connecting said first and second links.

7. An overload tripping switch as set forth in claim l, wherein each side of said second link comprises a perpendicularly extending tab, said housing comprising a longitudinal cam terminating in a perpendicularly disposed notch, said tabs being slidable along said cam and into said notch as said movable contact member is moved into engagement with said fixed contact, the engagement of said tabs with said notch preventing movement of the connected ends of said first and second links in a direction perpendicular of the longitudinal direction of said links by said connecting arm while permitting displacement of said links in said longitudinal direction.

8. An overload tripping switch as set forth in claim 7, wherein said housing comprises a pair of parallel plates and said cams comprise openings in said plates, said second link comprising a pair of spaced parallel members disposed between said plates and each having a tab extending perpendicularly outwardly therefrom through said openings and into engagement with said cam surfaces.

9. An overload tripping switch as set forth in claim l, wherein movement of said releasing arm to releasing position is controlled by a blocking arm, said heat sensitive member comprising first switch temperature responsive means associated with said blocking arm releasing said blocking arm from blocking relationship with said releasing arm in response to predetermined movement of said first temperature responsive means resulting from an increase in switch temperature, and second temperature responsive means associated with said first temperature responsive means regulating said predetermined movement thereof in response to changes in the ambient air temperature.

10. An overload tripping switch as set forth in claim 4, wherein said spring means disposed in said connection between said first link and said movable contact member comprises a leaf spring.

References Cited in the file of this patent UNITED STATES PATENTS (Addition to No. 806,157)

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