US2872543A - High load current switch - Google Patents

Description

Feb. 3, 1959 R. L. CLARK 7 I I HIGH LOAD CURRENT SWITCH Filed Dec. 25, 1954 3 Sheets-Sheet 1 5455321. (MW/r R. L. CLARK HIGH LOAD CURRENT SWITCH Feb. 3, 1959 3 Sheets-Sheet 2 Filed Dec. 23, 19 54 0 2 7 6 a 107 3 a w ff Tm, 4 a w k g4 w z 7,, L 1% m WW WW1! x 4 u I a 1 @ii WILHIIL a 0 v w 2 u w Wm m wvfli: .l- J 2 WH r I a a w E. a k 4 0/, 6/ w W a 0/0 6 k r l J INVEN R. /%i'/ liar/v4 6219/? aria/W5) nited States HTGH LOAD CURRENT SWITCH Robert L. Clark, White Plains, N. Y., assignor to Ward Leonard Electric Co., Mount'Vernon, N. Y., a corporation of New York This invention relates to electric switches and particularly to the contact assembly and-associated supporting members.

Electric switches readily carry overload currents within a given percentage of the rate of current for substantial periods of time without damage to the contacts. However, electric switches, particularly with butt type contacts, are damaged when a short circuit current or a current in the order of a short circuit current passes through the contacts even for brief periods. On occurrence of a short circuit surge or similar excessive current the contacts tend to separate thereby reducing the contact pressure and may completely separate creating an arc. The contacts become overheated and weld together rendering the switch inoperative. This fusion of the contacts is objectionable since the switch cannot be opened to isolate defective equipment producing the short circuit or ex cessive currents and is rendered useless for further service. Immediate switching is often required to continue operation of the equipment; It is therefore desirable to be able to maintain the contacts closed on short circuit currents and still be able to support the contacts on cessation of the currents so that the control of normal or short circuit currents is maintained by the appropriate equipment.

An object of this invention is to maintain closure of and prevent welding of the contacts of an electric switch during the passage of an excessive current.

Another object of the invention is to provide a contact assembly which will increase contact pressure and decrease contact resistance during short circuit currents.

Another object of the invention is to prevent magnetic forces of the current carrying members of a multiple electric switch from distorting the contact assembly and opening the contacts when carrying short circuit current.

A further object of'the invention is to provide a multiple electric switch that will withstand short circuit currents and'is simple and rugged in construction and has a compact arrangement of the parts.

Other and further objects of the invention will be apparent from the following description taken in connection with the drawings, in which:

Fig. 1 is a side view ofthe electric switch;

Fig. 2 is a sectional view of the switch taken aiong lines 2-2 of Fig. 1.

Fig. 3 is a sectional view of the electric switch taken along lines 3-3 of- Fig. 2. and an auxiliary sectional view of the chutes taken along lines 3a-3a;

Fig. 4 is an end view of the switch actuating member;

Fig. 5 is a sectional view along lines 5-5 of Fig. 2;

Figs. 6 and 7 are fragmentary viewsof a supporting rod;

Fig. 8 is a sectional view of a blowout coil and mounting; and

Fig. 9 is a front view of a portion of a common terminal and connector.

In the drawings a multipl'e'pole double-throw electric 2,872,543 Patented Feb. 3, 1%59 Pine switch is shown with two sets of contact assemblies. Each set has three pairs of contact assemblies with each pair comprising a movable contact assembly and a fixed contact assembly. The movable contact assemblies of one set are back to back to the respective movable contact assemblies of the other set. Each pair of contacts and the associated elements are the same in both assemblies and therefore a detailed description of one pair of contact assemblies is given and a description of the contact assembly in back to back relation is also given to illustrate the relationship of the two sets of the assemblies. The reference numerals for like parts of one set of contact assemblies are the same except for the sub-numerals 1 and 2.

In Fig. 3, the fixed contact 10 is connected by the bar 11 through the blow-out coil 12 to the terminal 14. The fixed contact is engaged by the movable contact 15 which is connected to a common terminal 16 by means of a laminated flexible copper connector 17. On the other side of the switch, the other contact assembly comprises a fixed contact 26 connected by a bar 21, blow-out coil 22 to the terminal 24. The movable contact 25 is connected to the common terminal 16 by means of a laminated flexible copper connector 27.

The electric switch is preferably mounted on the steel framework 31 containing the operating equipment such as the electric motor solenoids and the like. The contact assemblies are supported by triangular shaped supporting members 33, 34,- 35,36, rigidly attached to the framework 31 and having beams 37, 33 extending respectively between members 33, 34 on one side and 35, 36 on the other. The members 34, 36 are mounted along opposite longitudinal edges of the framework 31 to form a space therebetween, Fig. 2. The insulated supporting rods 43, 44, 45 extend between the plates and are securely fastened at their respective ends to the plates 33 and 35 to support the contact assemblies. The members 33 and 35 at the other end of the framework 31 are similarly spaced'and have similar insulated rods 40, 41, 42 extending between them with the respective ends fitted in the members 33 and35. An insulated rod 46 extends between the beams 37, 38 to support the common terminals. The members 33, 34, 35, 36 and beams 37 and 38 are preferably made of steel.

The rods 46), 41, 42, 5, 44, and 46 are similar in construction. The rod 46 has a steel center portion ide with a rectangular shape with pin 36b fitted into holes in the beams 37 and 38- (Fig. 6). A cylindrical threaded portion 46c extends through the beam and has a nut a"; threaded thereon to securely seat the pin 36b in the hole. An insulating material43 is formed around the rectangular portion 46a to insulate the common terminal 16 from the supporting metal structure. The rods 46, 41, 43, 44 are similarly securedto the supporting members 33, 35" and 34, 36 respectively. The-ends of the rods 4-2 and 45 are pivotally mounted in the respective members so that the contactslS and 25 may be moved into and out of engagement with respective contacts it and 20. The stud shafts 5t 51 of the rods 42, 45 pass through the supporting members 33, 34 with arms 52, 5'3 securely fastened thereto by pins 5- 1, 55 extending respectively through the shafts 50, 51 and arms 52, 53 (Fig. l). The arms 52, 53 are pivotally connected at the other end to the link-56 so that the arms 52, 53 are actuated together by the link 55. A cam 537 (Fig. 5) is securely fastened to a shaft 58 rotatably supported between the spaced plates at), 61. The plate 60 is securely fastened by welding or other suitable means to the framework 31 and the plate 61 .is U-shaped with flanges 62, 63 (Fig. 2) secured to plate 60. by bolts passing through the flanges andthreaded into the plate 69 and into the framework 31 at the lower end. The cam 57 is fitted between and engages spaced rollers 65, 66 mounted on the link 56. As the cam 57 is rotated it presses against one of the rollers and forces the link 56 in one direction or the other depending uponthe direction of rotation of the cam 57. A detent cam 67 is also securely fastened to the shaft 58 and has indents 7h, 71, 72, 73 (Fig. 4) into which the rollers 74, 75 are pressed by spring 76. The rollers 74, 75 are intermediately mounted on levers 77, 78 respectively, pivotally mounted at one end to the plate 61 and at the other end are connected by the spring 76 which is normally under tension pressing the rollers against the detent cam. As the shaft 53 rotates, the rollers 74, 75 move out of engagement throughone set of opposing indents. In this embodiment, the indents 71, 73 are diametrically opposed and the indents 7t, 72 are diametrically opposed at right angles to the indents 71, 73. The indents'71, 73 lock the contacts 19 and 15 together and the indents 70, 72 lock the contacts 29, together. The shaft 58 is rotated by means of a handle 86 rotatably mounted on the shaft 58 (Figs. 1 and 2) and has a stub 81 with notches 81a, 81b for engaging the arms 82a and 82b of the helical spring 82 positioned around a sleeve 34 fastened to the shaft 58. A plate 85 has spaced arms 85a, 85b, 85c extending parallel to the shaft 58. The stub 81 engages either the arm 82a or 82b of the spring 82 depending upon the direction of actuation by the handle 8%. When the stub 31 engages the arm 82a and unseats it from the notch 81a the spring is placed under tension and the handle 80 turns the arm 82a for nearly the full arc of rotation of cam 57 until it engages the arm 85a and unlocks the rollers 7 5, 75 from the indents 73, 71 so that spring arm 32b tensioned against arm 85b will further rotate the shaft 53 and complete the actuation of the cam 57 in the same direction to seat the rollers '74, 75 in the indents 72, 7d respectively. A slot 86 is provided through link 56 to per mit the link to be moved in relation thereto. cessive turns or rotations of the shaft 58 by the handle 80 the contacts 15, 25 may be moved in and out of engagernent with the respective fixed contacts. The arms 52, 53 are secured by the link 56 to stubs t 51 in such a manner that when contact is in engagement with the fixed contact 10 the contact is out of engagement with the contact 21) and similarly when contact 25 is in engagement with contact 20, the contact 15 is out of engagement with contact 10. The cam 57 and detent cam 67 provide an intermediate position in which both contacts are locked open.

As best illustrated in Fig. 3, the terminal 14 is yokeshaped comprising angular straps 14a and 14b riveted to conductor 19 at one end and held tightly clamped on the bar by the bolt 90 extending through strap 14b and threaded into the strap 14a. The blowout coil 12 is positioned below the terminal 14 and connected thereto by the conductor 19. The blowout coil 12 is wound around a tubular insulator 93 mounted on a steel rod 94 which is attached at respective ends to the beams 37 and 38 by appropriate means magnetically isolating the coils 12 from the beams 37, 38 and supporting means 33, 35.

On the other side of the switch the terminal 24 and blow-out coil 22 are of-a similar construction with an interconnecting conductor 29. The blow-out coils 12 and 22 are similarly mounted. In Fig. 2, a detailed view of the mounting of coil 22 is shown. A detailed illustration of the mounting of the blow-out coils is shown in Figs. 2 and 8. The rod 95 has threaded portions 166, 167 extending through openings 169 and 168 in beams 38, member 36 and beams 37, member 34 at respective ends of the rod. The magnetically isolating mountings at each end of the rod are similar and fit in the openings 16%, 169. The mounting has a small insulating washer 170 fitting in the opening-168 and a larger insulating By suc-.

washer 171 engaging the beams 37. The rod extends through the washers and the threaded portion has nuts 172, 175. The nut 172 has a lock washer 174 engaging a steel washer bearing against the insulating washer 171. The nut 172 tightens the washers 1713, 171 against the nut 175 to securely position the washers on the rod 95. The mounting at the other end has insulating washers 181 and 182 magnetically isolating the rod from the beam 38 with a nut 173 securely holding the insulating washers in position against the nut 185. Each of the blow-out coils is mounted on a steel core 178 and an in sulating sleeve 184 around which the blow-out coil 22 is wound. The core 178 is reduced at each end to form shoulders for the plates 186, 186a. The cores of the other blow-out coils are similarly constructed. A brass washer 188 prevents axial movement of the plate 136. Insulating washers 191, 192 are provided on each end of the sleeve 184 to form insulating spools to electrically separate the coil and the plates 186, 186a. The blowout coils 22a, 22b are similarly mounted as are blowout coils 12, 12a, 12b of the other contact assembly. The end of the coil is electrically connected to the contact bar 11. The bar 11 is securely fastened to the insulated rod 41 by suitable means such as the strip 96 and bolts 661. The contact bar 11 extends normal to the bar 4-1 and has the contact 10 electrically fastened to the bar by a bolt or the like for forming an integral member therewith. The contact 11) and bar 11 are secured to the bar 41 to transmit the pressure applied by the movable contact in this embodiment, the end of the bar 11 has a step into which the contact 10 fits and a notch fitted over the bar 41. Thus a current path is provided between the terrninal 14 and the contact 19.

The common terminal 16 is a fork-shaped member comprising two stiff metal strips 117 and 118 with angle portions 117a, 113a respectively, fitted around the square rod 46 rigidly mounted in the beams 37 and 38. The strips 117, 118 are clamped to the rod by the rivet 119 below the rod 46 and the bolt 12% passing through the strip 118 and threaded in the strip 117. The strips are spaced from the contacts 15 and 25 and preferably aligned with the contacts 10 and 20 so that the magnetic force between the strips and contacts is aligned. The strip 117 has a portion 117k vertically positioned and a portion 1170 at an angle thereto.

The strip 118 has a portion 113i) contiguous with strip 11711 and a portion 3118c at an angle to the portion 117c. The strips 117 and 118 provide a good current path between the terminal 16 and laminated copper connectors 17 and 27.

The contacts 15 and 25 are mounted on pivoted arms and 191 and are electrically connected to the strip 117, 118 of the common terminal, respectively, by the laminated copper connectors 17 and 27, respectively. The arm 100 pivotally supporting the movable contact 15 comprises a member 100a secured to the rod 42 by a yoke 102 having bolts 103 passing through the member 100a and threaded in the yoke 102 or pivotally mounted by other suitable means. The member 10012 is attached to an intermediate portion of the member 100a by the hinge 104 and flexibly connected by the:helical spring and spring pin 106.

At the other end of the member 10Gb there is an angle 116 with a finger 116a. The L-shaped contact 15 fits in this angle and is seated against finger 116a and secured to the angle by means of a bolt 114 fastened through the contact 15 and threaded in the angle 116. The contact pressure applied by the arm 100 is transmitted to the contact 15 through the finger 116a and the bolt 114. The contact 15 is electrically connected to the common terminal through the laminated copper connector 17 secured to the contact 15 by means of a lug 113. The lug 113 is of a generally U-shape with one leg secured to the contact 15 by the bolt 114 and the other leg 113a connected to the 'higher contact resistance.

laminated copper connector 17. The laminated copper connector 17 is held against the member 10012 by the spring pin 106 and a washer106a secured thereto. The leg 113a is at a downward angle to the finger 116a and the laminatedcopper connector 17 is fastened at a point below the angle 116and-the finger 116a on'the member 10012 so that the strap hangs downwardly or adjacent to the arm 100. The other end of the'strap issecuredto the portion 1175 of the common terminal 16'at a point generally opposite to the contact 15 andextends downwardly'along the portions 117b, 117c'so that the flexible strap 17 hangs in a generally 11- orloop'shape in'the same plane.

The spring 1115 is seated in'the cupped washers 107, 103

at a respective end. The spring pin passes through the longitudinal axis of the washers and spring and through an elongated opening 109 in 10017 anda hole in100a to permitthe freemovement of the shaft through both members Mile and 1116/2. The spring pin is secured by a cotter pin 30 at oneend. The other end has a head 110 pressing against thewasher 107. Thus as'the shaft 42 in Fig. 3 is turned counterclockwise from an open to a closed'position of the contacts, the members 100a and 10911 are moved counterclockwise; The contact 15 en'- gages contact 1t1'and the member 100a'continues to rotate separating the members-100a and100b by pivoting on the pins 111 on the endof member 100bin' the fingers 112. The member 10110 compresses the spring against the head 1111 and betweenthe washers 107, 108 so that a uniform pressure is applied by the cotter pin 30 and washer .itieaand therebyto the contacts and through the member 1011a. mal currents to provide adequate current transfer Me On occurrence of an excessive current such as by a shorecircuit, the current through the'ilexible connector 17 producesa magnetic field around the strap. Since the field density of the magnetic flux is higher'on the inside of the loop than on the outside, the field exerts a pressure forcing the flexible connector to straighten. The arm 10% and portions 117 and 1170 of the terminal 16 retain the flexible connector 17 in a generally U-shape as illustrated in Fig. 3.

The forces exerted by the flexible connector17 are transmitted through the member 100a and the portion 116a to the contact IS'Which is applied to the contact or current transferring surfaces 10a, 15a. The contact 10 applies a counter resisting force through thefbar 11 and endrod 411 The strips 117b and'117c are'rig'id' and apply a torque to the rod 46; The rod" 46 is keyedinto the beams 37 and 38 to resist any turning so the rod 46 firmly holds the strip .117 in position. The increase in contact pressure between the contacts 10 and 15 reduces the resistance to the flow of high current and lessens the heat generated in the contacts. The contacts and the associated bars and members transmit the heat from the surfaces and dissipate it.

The contact pressure increases with the increase in current and is created instantaneously with the increase in current. The contacts do not initially separate on occurrence of the short circuit producing an arc and then close but remain continuously closed so that there is no burning of the contact surfaces or welding together. Similarly the strap 27 holds the contact or current transferring surface 25a of contact 25 in firm engagement with the contact or current transferring surface 29a of contact at a low contact resistance.

Rectangular members 140 and 141 are secured on opposite sides of the portions 117a, 1180 and project on each side of the flexible connectors 17 and 27 (Fig. 7). The projecting ends hold the flexible connectors from lateral movement so that they will not disengage from the members 117 and 118 by the magnetic forces created between the flexible strap on the passage of an excessive current through them. The flexible connectors 17, 17a, 17b of a set of contact assemblies are parallel and the This pressure is sufficientunder normagnetic forces encircling these connectors tend to force the connectors laterally. As shown in Fig. 9 rectangular members 140-1, 141-1 and 1411-2, 1411-2 are provided on members 117-1, 118-1 and 117-2, 118-2 respectively to hold the straps 17-1, 17-2.

The arm 101 and strap 27 are similar in construction with the strip portion 11%!) contiguous to the portion 11717 and the portion 1180 bent at an angle from portion 1170 and towards the arm 101. The arm 101 is shown in the open position with the spring 122 forcing the members and 124 together through the cupped washer 125 engaging the head 126 of the spring pin 127 and at the other end by a flat washer 128 held by cotter pin 129. The other end of the spring 122 is seated in the cupped washer 134) and presses on the member 123. The member 124 has an angle 131 holding the contact and applying pressure in cooperation with the bolt 132. The strap 27 is connected to the contact 25 by the lug 133 and bolt 132 passing throughthe lug contact 25 and threaded in the angle 131.

The contact assembly has arc chutes 16a? positioned above the contacts 21), 25 to form an arc passage 163 therethrough. The chute 160 has plates 186, 186a rigidly fastened to the side Wal1s'162, 164 at one'end and having slots 194, 194a fitting over'the shoulders of the core 178 to detachably mount the arc chute. The other chutes 161 -1 and 1619-2 have plates 186a, 1361: and 18612, 1516c. The arc'chutes 160 169-1 and 1611-2 are fastened to the frame'to secure thechutes to the switch and prevent pivoting about the rod by the brackets 199 fastened to the beams 37, li and to the long bolts 2%, 201 extending through the chutes and nuts 2 .12, 263 threaded thereon. The chutes 143 are similarly retained by brackets 204, 21 5 andbolts 206, 207 secured by nuts 208, 269. The chute 1 3 has plates 151, 151a fitting on each side of the'insulating spool 94. The wall 1 37 is angularly positioned so that the passage or chute 14 converges upwardly and the lower bottom edge of the wall 147is spaced from the contact 15 so that the arm 'rnay'rotate freely from thecontact 10 and provides for an air inlet into the bottom of the chute.- The side walls 146, 14301? chute 143-and walls 162, 164'of chute 160 extend downwardly below the contacts 119 and 15 so that adjacent pairs of contacts of the set of contact assemblies are separated by an insulating barrier to prevent arcing between pairs of contacts. Arc chutes over contacts of theset of contact assemblies including contacts 10, 15 are not shown but are similar to are chute 143.

In the preferred embodiment illustrated in the drawings, and particularly in Fig. 2, an electric switch embodying the invention is shown adapted to a three-phase system. The contact assemblies are identical for each phase. In Fig. 2 there is shown the contacts 20-1 and 20-2 for the additional phases with associated blow-out coils 22-1 and 22-2 and terminals 24-1 and 24-2. The invention can be readily adapted to two-pole or single pole systems.

Modifications may be made in the invention by having a horizontal supporting member engage the bottom of the U-portion of the straps 17 and 27 to further resist the straightening action of the straps. The members similar to angular members 1170 and 1180 may be mounted on the arms 100 and 1111 to form the confining or restricting structure for the straps 17 and 27 respectively. In the latter modification the retaining members and 141 may be mounted on extended members 1171; and 118b and project towards the respective arms 100 and 101 or similar type members may be mounted and moved with arms 100 and 101.

Various other modifications and changes may be made in the invention without departing from the scope of the invention as set forth in the appended claims.

I claim:

1. An electric switch comprising a first contact, a secend contact movable into engagement with said first contact with a backing portion extending laterally to the direction of movement, a fixed member spaced rearwardly from said second contact and extending laterally to the direction of movement of said second contact, a flexible conductive strap connected to said second contact and formed in a loop with a portion normally adjacent said second contact and a section adjacent said fixed member, said strap bearing against said second contact and said member on occurrence of excessivecurrent therethrough to exert pressure holding said second contact in engage ment with said first contact.

2. An electric switch as claimed in claim 1 wherein said first contact has a current transferring surface and said second contact with said portion comprises an arm pivotally mounted at one end and having a current transferring surface at the other end engaging the current transferring surface of said first contact and firmly held with a low contact resistance on occurrence of an excessive current therethrough.

3. An electric switch as claimed in claim 2 wherein said fixed member is securely fastened in relation to said first contact.

4. An electric switch as claimed in claim 3 wherein said first contact, said second contact, said fixed member and said strap interconnecting said second contact and said fixed member are substantially aligned in the same plane and said fixed member has holding means to prevent lateral movement of said strap and to maintain said alignment.

5. An electric switch comprising a frame, a first contact and a second contact, said first contact securely fixed to said frame, an arm having said second contact mounted at one end and at the other end pivotally mounted on said frame to move said first contact in and out of engagement with said first contact, a fixed member rigidly secured to said frame in alignment with said fixed contact and said movable contact, a flexible laminated electrically conductive strap formed in a loop in alignment with said fixed contact and movable contact and bearing against said arm and said fixed member to exert pressure holding said contacts closed on passage of an excessive current therethrough.

6. An electric switch comprising a frame, a plurality of contact assemblies in side-by-side relation each having a first contact and second contact movable into engagement with said first contact and a fixed member spaced rearwardly from a respective second contact, a conductive strap formed in a loop with a portion nearly adjacent saidsecond contact and a portion adjacent said fixed member, said strap bearing against said second contact and said fixed member on currents in the order of short circuit currents to exert pressure on said contacts, said straps of said contact assemblies in side-byside relation adapted to pass a current in the order of a short circuit current, each of said fixed members having a holding means extending on each of the respective straps to prevent lateral movement of the said straps due to electromagnetic forces between said straps and hold said straps against said fixed members on occurrence of a current in the order of a short circuit current.

7. An electric switch comprising a frame, a contact assembly having a pivotally mounted arm, a fixed contact mounted on said frame and a movable contact mounted on said arm, a fixed member in the plane of said arm and with said arm between said fixed member and said fixed contact, a flexible contact strap connected to said movable contact bearing against said arm and said fixed member to hold said contact in engagement on passage of a short circuit current, a pair of terminals on the other side of said contacts from said arm and strap, connecting means between said terminals and said movable contacts and said strap, said connecting means positioned on the other side of said contacts to isolate the magnetic forces produced in said connecting means from said strap.

8. An electric switch comprising parallel supporting members separated to form a space therebetween, three horizontal insulated bars mounted between said members and vertically stacked in spaced relation, a terminal mounted on said top bar, a movable contact mounted on said intermediate bar, said lower bar being pivotally mounted in said supporting members, an arm securely mounted on said lower bar at one end and supporting a contact movable in and out of engagement with said fixed contact and connecting means between said fixed contact and said terminal to isolate the electromagnetic forces produced in said connecting means from said arm.

References Cited in the file of this patent UNITED STATES PATENTS February 3, 1959 Patent No, 2 872 543 Robert Clark that error appears in the printed specification that the said Letters It is hereby certified requiring correction and of the above numbered patent Patent should read as corrected below.

contact line 35 for first contact read second movable Column '7,

second occurrence, read oolumn 8 line 36, for "fixed" Signed and sealed this 2 t L day of May 19590 ttest: 'v ,T 1

KARL AXLINE ROBERT (J. WATSON Commissioner of Patents Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE QT CORRECTION Patent N00 2 872 543 February 3, 1959 Robert L, Clark s in the -printed specification ied that error appear and that the said Letters It is hereby certif of the above numbered patent requiring correction Patent should read as corrected below.

second contact Column '7 line 35 for "first contact" read column 8, line 36 for "fixed, second occurrence, read movable Signed and sealed this 26th day of May 1959a SEAL) ttest: f I I KARL a}, AXLINE ROBERT c.- WATSON Commissioner of Patents Attesting Ofiicer

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