US3639715A - Fixed and movable contact structure for disconnect switches - Google Patents

Abstract

An insulation carrier of one or more pairs of similar U-shaped contact members is movable toward and from one or more pairs of spaced parallel flat fixed contact blades so that a pair of said blades are engageable and disengageable by a pair of said movable contact members, with the ends of the one of the U-shaped members engaging the outside surfaces of said fixed contact blades while the ends of the other of the U-shaped members engage the inside surface of said blades, causing electromagnetic forces incident to heavy current flow to be concentrated around the movable contacts and to create a pinching effect against the fixed contact blades in fully engaged position. The outer of the pair of movable contacts is longer so that its ends engage the fixed contact blades first, creating (prior to the pinching effect) a weakening of their pressure against the fixed contact blades during initial engagement to facilitate movement into full engagement in case of heavy current flow.

Description

United States Patent Christensen et al.

[54] FIXED AND MOVABLE CONTACT STRUCTURE FOR DISCONNECT SWITCHES [72] Inventors: Paul M. Christensen, West Orange, N.J.;

Robert J. Petitjean, West Simsbury, Conn.

[73] Assignec: Arrow-Hart, Incorporated [221 Filed: May 15, 1970 [21] Appl. No.: 31,363

[52] US. Cl ..200/166 E, 335/16, 335/195 [51] Int. Cl. ..Il0lh 1/54 [58] Field of Search ..200/166 E, 163, 170 A; 335/16, 335/195 [56] References Cited UNITED STATES PATENTS 761,533 5/1904 McKee ..200/166 E 3,083,271 3/1963 Lambert et a1... ....200/l62 X 2,179,737 11/1939 Frank ....200/170 X 1,586,682 6/1926 McCoy ..200/166 E 3,087,039 4/1963 Bachman ..200/166 E Feb. 1, 1972 ABSTRACT An insulation carrier of one or more pairs of similar U-shaped contact members is movable toward and from one or more pairs of spaced parallel flat fixed contact blades so that a pair of said blades are engageable and disengageable by a pair of said movable contact members, with the ends of the one of the U-shaped members engaging the outside surfaces of said fixed contact blades while the ends of the other of the U-shaped members engage the inside surface of said blades, causing electromagnetic forces incident to heavy current flow to be concentrated around the movable contacts and to create a pinching efiect against the fixed contact blades in fully engaged position.

The outer of the pair of movable contacts is longer so that its ends engage the fixed contact blades first, creating (prior to the pinching effect) a weakening of their pressure against the fixed contact blades during initial engagement to facilitate movement into full engagement in case of heavy current flow.

9 Claims, 8 Drawing Figures FIXED AND MOVABLE CONTACT STRUCTURE FOR DISCONNECT SWITCHES This invention relates to electric switch contact arrangements and constructions. More particularly, it relates to electric switch contacts used in heavy-duty disconnect switches for 60-100 ampere duty, although the invention is applicable to switches of other classifications.

BACKGROUND OF INVENTION In order for heavy-duty switches to be acceptable under the specifications used in industry, the switches are tested for performance on closure when a short circuit condition exits. Improperly designed switches can be destroyed in such tests by failure to withstand the action of the magnetic forces and heat and arcing incident to the abnormally high current flow during such conditions. In equipment improperly designed, these forces cooperate to tend to weaken contact engagement and hence tend to increase dilatorious action.

If the switch contacts are made sufficient contact pressure, or are provided with additional biasing pressure, to withstand electromagnetic forces during heavy current conduction short-circuit provide adequate pressure at all times to keep low the heat generated at the points of contact engagement, then it becomes difficult to open and close the switch.

An object of the invention is to provide an improved switch contact structure having high current-carrying capacity and utilizing the forces of the heavy currents and short-circuit conditions to maintain and increase strong contact engagement rather than to weaken, damage or destroy the switch contacts. A related object is to provide switch contact structure which reduces the heating of the contacts, incident to the flow of heavy current, by providing multiple points of contact engagement whereby each point carries only a fraction of the total current and hence reduces the degree of heating at each point.

Another object is to provide multiple current paths in achieving the aforesaid objectives.

Another object is to provide for delaying the utilization of the electromagnetic force action during the initial contact engaging action, as by sequential engagement of contact points and completion of multiple current paths, to avoid high contact pressure buildup until all contact surfaces are engaged.

Another object is to provide switch contacts which are strongly biased toward engagement but in which the bias is limited in such a way as to make contact closing easier.

Another object is to provide a switch having structural characteristics to achieve the foregoing objectives, which is made up of standard parts and can be made for various contact ratings by increasing the number of contact sets incorporated in the movable contacts.

Other objects and advantages of the invention will become apparent as it is described in connection with the accompanying drawing.

DETAILED DESCRIPTION In the drawing:

FIG. 1 is a fragmentary top plan view of stationary switch contact structure of one pole of a switch embodying the invention.

FIG. 2 is a longitudinal section view of a movable switch contact structure embodying the invention, one pole of the switch being adapted to engage a stationary switch contact of FIG. 1.

FIG. 3 is a longitudinal section view taken along line 3-3 of FIG. 1.

FIG. 4 is an end elevation view of the invention illustrated in FIGS. 1-3 with the movable switch contact partly engaged with the fixed switch contact.

FIG. 5 is a side elevation view of the invention as illustrated in FIGS. 1-4.

FIG. 6 is an exploded perspective view of some parts of another form of movable contact carrier and movable contact structure embodying the invention.

FIG. 7 is a transverse section view taken along line 7-7 of FIG. 6.

FIG. 8 is a transverse section view taken along line 8-8 of FIG. 6.

Referring to the drawing, the contact structures illustrated in FIGS. 1-5 are of a form that is used in disconnect switches that are designed to carry heavy current such as from 60 to I00 amperes in multipole feedlines. Such switches are operated by various types of mechanism of which the type ii lustrated in copending application Ser. No. 848,948, of Paul Christensen, filed Aug.'l I, I969, is only one example, wherein the movable contacts move rectilinearly to engage and disengage the fixed contacts. Although such mechanism are usually of multipole form, only one pole will be described herein since the other poles are duplicates of it.

The fixed contacts are mounted in a base 10 of suitable ceramic or molded insulation material that is formed as a block hollowed out and recessed to receive a first L-shaped stationary contact 20, stamped from heavy sheet metal, and a second L-shaped stationary contact 30, likewise stamped from heavy sheet metal. Contact 20 is mounted in a chamber 12 in an insulating base 10 on a ledge or raised part 14 of the bottom of the recess 12. One leg 22 of the contact 20 extends into the lower part or loop of a fuse clip 40 of conventional shape having a flat transverse part 42 with opposite side arms 41 and 43, shown broken away for clarity.

The leg 22 of the fixed contact 20 lies in and is secured to the transverse portion 42 of the fuse clip, and both are affixed permanently on the elevated portion of the base recess 12 by a screwbolt 46 which passes through a hole in the ledge from the bottom side of the base 10 and threads into a tapped hole in the leg 22.

The second fixed contact has a short leg 32 lying against the bottom of the recess 16 in the bottom surface of the base I0 near one edge and is secured against it by a screwbolt 26 passing through the bottom of the recess 12 of the-base and into a threaded hole in the short leg 32. The other leg 34 of the contact 30 is longer and extends upward through the recess 16 to the base chamber 12 parallel to the leg 24 of the first fixed contact in spaced relation.

For engagement with the fixed contactarms 24 and 34, pairs of movable contact members, designated generally by the numerals 50 and 60, are mounted in an insulating block 70 that is insertable into and a removable from the base chamber 12. The block and the contacts are shown in FIG. 2 poised above the base of FIG. 3. The contact carrier 70 is generally of rectangular form having two identical mating halves, each having recesses in one face for movable contact members such as 50 and 60.

Referring to FIGS. 2 and 4, the half 7 l of the insulation carrier is recessed in its upper part to provide a cavity in which is located the first U-shaped movable contact member (designated generally by numeral 50) in the form of a stamped sheet U-shaped bar having substantially parallel arms 52 and 54 joined by a transverse part 53. The tips of the arms each flare outwardly. The ends of the arms 52 and 54 extend downwardly outside the upper cavity or recess 7Ir into laterally open recesses in the sides of the carrier. The upper cavity opens into said laterally open recesses. These recesses are separated by a central partition or spine 71p running to the lower end of the carrier.

The movable contact 60 is similar to the movable contact 50 in shape but is smaller and its tips are flared inwardly instead of outwardly. Arms 62 and 64 of the inner movable contact are spaced from the arms 52, 54 of the outer contact a distance sufficient to receive between them the stationary contact blades 34, 24, respectively, as will be more fully described hereinafter.

To separate the transverse parts of the movable contact 50 from the movable contact 60 electrically, an insulating shim or plate 74 is positioned between these transverse parts 53 and 63. The insulation of the movable contacts 50 and 60 reduces magnetic heating of the contacts under load, enabling a high to their inner surfaces to minimize friction and facilitate the motion between the springs and the contact arms against which the springs press.

Inner backup springs 78 are provided for the inner movable contact 60 similar in purpose and structure to the outer spring 76, except that the inner spring arms are shorter and are located between the inner movable contact arms 62, 64, and the insulation partition 71p.

To maintain a minimum separation of the arms 62 and 64 from the arms 52 and 54, insulating spacing pins 75 and 75' arepositioned between the arms 52, 62, and 54, 64, respectively, at points midway along the length of those arms. Each pin is seated at its opposite ends in registering holes in the halves 71, 72, of the insulating block 70.

The spacing pins limit the movement toward each other of the movable contacts without affecting the contact pressure.

' The pins always maintain a sufficient spacing of the movable contacts to allow the fixed contacts to enter. .This characteristic also functions when electromagnetic forces act strongly to pinch the movable contact pairs together, such as during contact making under heavy current conditions, as further described below.

Since the spacing pins only limit the movement of the movable contacts toward each other, the strength of the contact pressure after contact engagement is not affected. The advantage of full-force pressure action for high contact pressure is maintained.

For the purpose of locating and maintaining in spaced position the movable contacts 50 and 60, a pin 73 passes through both of the parallel transverse parts 53, 63 of the movable contacts and through the shim 74. The pin 73 has its ends received in aligned grooves in the body of the insulating block above and below the transverse parts 53 and 63, respectively, of the movable contacts.

As has been above mentioned, the second half 72 of the movable contact block 70 is identical to the first half 71 and has mounted in it movable contacts which are identical to the movable contact above described. Likewise, backup springs identical to those just described are employed and spacing pins like the spacing pins75, 75 and a locating pin like the locating pin 73 and a spacing shim like the spacing shim 74 are also provided.

Thus when the halves 71, 72 of the carrier are put together with their open faces in register, the cavities enclose the upper U-shaped portion of the movable contacts 50 while the lower or free ends of their contacts extend into the open recesses at either side of the central partition 71p and 72p.

In order to keep the movable contacts 50, 60 in the first half 71 of the movable contact carrier 70 physical and electrically separate from the like contacts in the other half 72, a fiat strip 79 stamped from sheet insulation in the form illustrated in FIG. 2 is positioned midway along the length of the contacts in such a way as to lie against and across the edges of all of the movable contact members. The strip is held in place between the two halves 71 and 72 when they are secured together by screwbolts 65 after all of the parts have been assembled in the carrier.

For moving the contact carrier by a switch-operating handle (not shown) or the bail (not shown) of the switch-operating mechanism, a pair of parallel, stamped sheet metal hookshaped members 77 are secured in recesses formed in the outside srirfacesof the two halves of the insulating contact carrier by one of the screwbolts 65 so that when an operating member is inserted in the hook formation, the contact carrier may be moved rectilinearly upwards and downwards to cause contact engagement and disengagement.

From the foregoing, it will be understood that when the contact carrier is inserted into the cavity in the base, the movable contact members 52 and 62 will engage the opposite faces of the upstanding fixed contact blade 24; likewise, the movable contact members 54 and 64 will engage opposite faces of the other fixed contact member 34. Since the movable contact sets 50 and 60 are provided in pairs, 50 and 50' and '60 and 60, as may be best seen in FIG. 5, the current may be conducted in two paths which are parallel to each other from the fixed contact member 24 through the two sets of movable contact members 50, 6 0, to the fixed contact 34. Thus each of the movable contact members 50 and 60 becomes a conductor, carrying current which has an electromagnetic field surrounding it. The lines of electromagnetic force surrounding the contact 60 between the contact 60 and the contact 50 will oppose each other between those two contacts, thus causing a concentration of lines of electromagnetic force on the outside of the contact 50 and on the inside of the contact 60. These lines of force will tend to unify into one fieldsurrounding both of the contacts 50 and 60 and thus tendingto press or. pinch together the arms of the movable contacts against the fixed contact blades, particularly strongly during heavy currents or short circuit conditions. In other words, the electromagnetic force generated by the overload or short circuit current will exercise a very strong squeezing effect upon the two movable contact members 50 and 60, causing them to very firmly grip fixed contact blades at the time when it is most desirable to maintain contact pressure and engagement with the strongest possible force.

As the movable contacts are moved out of engagement with the fixed contacts, the arms of the outer movable contact 50, being longer than those of the movable contact 60, will remain in engagement with the fixed contact blades; and any arcing will take place between the fixed contact blades and the movable contact arms 52 and 54, thus tending to keep the arms 62 and 64 of the inner movable contact clean and bright.

As the movable contacts are moved into engagement with the fixed contact blades, the contact arms 52, 54 (being longer than arms 62, 64) will engage the fixed contact blades 34, 24 first. This creates an electromagnetic field around arms 52 and 54 with the flux lines in the same direction between them, thus casing a concentration of flux which tends to push the arms away from each other and hence away. from the fixed contact blades, producing a reduction in pressure of the movable contacts against the fixed contacts. Under ordinary current fiow, this force is not of great significance, but on heavy or shortcircuit current flow, the lessening of pressure makes contact engagement easier. This condition exists only a fraction of a second due to the high velocity of closing movement and the short distance of travel until the inner contact arms 62, 64 engage the fixed contact blades. Thereupon the magnetic field conditions change to create the pinching efi'ect of the contact sets 52, 62 and 54, 64 upon the fixed contact members 34 and 24 as above. Experiments have shown that when the movable contacts are of the same length and engage the fixed contacts at the same time under short-circuit conditions, the friction created by the pinch effect is so strong that the movable contacts cannot be moved into fully engaged position. Instead, they tend to weld to the tips of the fixed contacts.

Because of the flaring of the ends of the movable contacts and the bevelled ends of the fixed contacts, the flat side of the flared end of the movable contact engages along its length with the fixed contact blade, providing a large contact area at the outset to keep current density to a minimum during the initial surge of current.

Referring to FIGS. 6-8 another form of insulated carrier for the movable contacts is illustrated having a central body 80, and two sideplates (only one is shown, see FIG. 6), one for each side of two opposite identical sides of the central body 80. The central body is symmetrical about a central longitudinal plane and preferably is made of molded insulation, but the invention is not limited as to material.

The central body is formed with a platelike flat longitudinal partition part 81 having a lateral tubular enlargement 81a near one end which is hollow to afford a passage 81p for a securing bolt. On the other end of the partition 81 is formed a head structure composed of parallel similarly shaped walls 82 and 83, each being U-shaped with the inner wall 83 being within and spaced from the outer wall 82. The U-shaped walls are connected together midway of their depth by a transverse partition or web 84, the web extending entirely across the head structure and upwardly from the middle of the partition part 81 in a plane transverse thereto.

The spacing of the inner and outer walls 83, 82 provides between them a U-shaped channel 85 within which is seated a U-shaped movable contact 150 similar to the contact 50 in the form of FIG. 2. As in the FIG. 2 form, a U-shaped backup spring (like 76 in FIG. 2 but omitted from the illustration in FIG. 6) is used. The spring fits in the channel 85 alongside of the contact 150 in the same way as in FIG. 2.

For locating the contact 150 and its backup spring (instead of the pin 73 of FIG. 2), there is provided in the FIG. 6 form a notch 151 in the center of one edge of the transverse part 153 of the contact. The notch receives a nub 86 protruding from the partitioning web 84 into the channel 85, thus to maintain the position of the contact, when assembled, in its predetermined desired location.

An inner U-shaped movable contact 160 (like contact 60 in FIG. 2) is provided in the FIG. 6 form. This inner contact, when assembled, is positioned within the embrace of the U- shaped wall 83 and engages the inner surfaces of the top and sides of that wall, while said wall serves to separate and insulate the inner and outer movable contacts in lieu of the pins 75, 75' of FIG. 2. A boss 87 is formed integrally in the carrier body 80 within the area embraced by the U-shaped inner wall 83 and having a flat side facing the transverse part of the wall 83. The contact 160 has a notch 161 to receive a nub like 86 for the purpose of maintaining contact 161 in assembled position.

A backup spring (not shown but like 78 in FIG. 2) is used with contact 160 and is located with the embrace of contact 160, as in FIG. 2.

The provision of the central transverse web or partition 84 causes division of the contact carrier 80 into two identical 0ppositely facing configurations so that two sets of inner and outer contacts 150, 160 may be mounted in the carrier, in insulated relation, the two sets being separated by the web 84.

To hold the two sets of contacts in their respective assembled positions in the carrier, identical sideplates 90 (one of which is shown in FIG. 6) are provided to be secured against opposite sides of the body 80.

The sideplates 90 fit flatly against and over the open faces of the central body and are secured by bolts (not shown) passing through apertures 91, 92 in the plates in coaxial relation to the passages 81p, 87p in the central body. The outer edges of the movable contact members abut the inner surfaces of the plates 90, and the contacts are thus held in place in their respective recesses in the central body 80.

A pair of parallel longitudinally extending ribs 93, 94 may be provided in spaced relation on the outside faces of each of the plates 90 which serve to strengthen the plates but mainly to guide the motion of the contact carrier and movable contact members during movement between contact engaging and disengaging positions.

The contact carrier of FIG. 6 is moved, as in the previously described form of FIGS. 2, 4 and 5, by the engagement with switch-operating means of a pair of parallel hook-shaped members, like 77, secured between the top ends of the ribs 93, 94 by the securing bolt which passes through apertures 91 and passage 87p.

Many modifications within the scope of the invention will occur to those skilled in the art; therefore, the invention is not limited to the precise form and the configuration of parts as illustrated and described.

What is claimed is:

1. An electric switch comprising an insulating base, a pair of fixed contact members mounted on said base, a pair of movable contact members engageable with and disengageable from said fixed contact members, an insulation carrier supporting said movable contact members in electrically separate relation, said movable contact members engaging different faces of said fixed contact members and creating proximate parallel current paths with their fields of electromagnetic force cooperating to create a pinching effect of said movable contact members against each fixed contact member to increase the force of engagement of said movable contact members against each fixed contact member incident to heavy current flow, and in which one of said movable contact members engages said fixed contact members before the other and is shaped to create a concentration of the field of electromagnetic force tending to decrease the pressure of said one contact member against said fixed contact members during heavy current flow prior to engagement of said other movable contact member with said fixed contact members.

2. A electric switch as claimed in claim 1 wherein said movable contact members are V-shaped with one inside the other and the outside movable contact is longer than the inside movable contact for engagement of the fixed contact members prior to engagement by the inside movable contact.

3. An electric switch as claimed in claim 2 having means biasing each of said movable contact members individually toward said fixed contact members in contact-engaged position.

4. An electric switch as claimed in claim 1 having means biasing said movable contact members toward said fixed contact members in contact-engaged position.

5. An electric switch as claimed in claim 1 wherein said movable contact members are U-shaped with one inside the other and interengaging means are provided between the transverse portions of said movable contact members and said carrier for positioning said contact members in said carrier.

6. An electric switch as claimed in claim 5 having insulating means between said movable contact members maintaining them separated.

7. An electric switch as claimed in claim 1 having insulating means between said movable contact members maintaining them separated.

8. An electric switch comprising an insulating base, a pair of fixed contact member mounted on said base, two pairs of movable contact members engageable with and disengageable from said fixed contact members, an insulating carrier on which said pairs of movable contact members are mounted, said carrier having a unitary block of insulation with opposite faces, each of which has recessed to receive one pair of said movable contact members, means on said carrier insulating one pair of said movable contact members from the other pair, insulating plate means secured over said recessed faces and holding each pair of said movable contact members in its respective recess, each pair of said movable contact members engaging opposite faces of said fixed contact members and the fields of electromagnetic force cooperating to create a pinching effect against each of said fixed contact members when engaged fully, one of said said movable contact members of each pair engaging said fixed contact members before the other and is shaped to create a concentration of the field of electromagnetic force tending to decrease the pressure of said one movable contact member against said fixed contact members during heavy current flow prior to engagement of said other movable contact member with said fixed contact members.

9. A switch as claimed in claim 8 having means biasing each of said movable contact members individually toward said fixed contact members in contact-engaged position.

Patent-No. 3,639,715 Dated February 1, 1972 Invento1:(s) Paul'M. Christensen and Robert J. Petitjean It' is certified that error appears in the above-identified patent and that said Lepters Patent are hereby corrected as shown below:

Column 1, line 24, "short-circuit" should be deleted and i and to inserted instead.

Column 6, line 23, "V-shaped" should be U-shaped Signed and sealed this 8th day of August 1972.

(SEAL) fittest:

EDWARD M.FLETCHB5R,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents (3)2 5 UNZEFED STATES m'115r-41. armor Patent No 3,639 ,715 W D tfilil February 1, 19 72 Inventor (5) Paul M. Christensen and Robert J. Petitj'ean It' is certified that error appears in the above-identified patent and that said Letters Patent are. hereby corrected as shown below:

Column 1, line 24, "short-circuit" should be deleted and -.-.and to inserted instead. Column 6, line 23, "V-shaped" should be U-shaped Signed and sealed this Bthday of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHB1R,JR. ROBERT GUTTSCHALK Attesting Officer Commissioner of Patents

Claims (9)

1. An electric switch comprising an insulating base, a pair of fixed contact members mounted on said base, a pair of movable contact members engageable with and disengageable from said fixed contact members, an insulation carrier supporting said movable contact members in electrically separate relation, said movable contact members engaging different faces of said fixed contact members and creating proximate parallel current paths with their fields of electromagnetic force cooperating to create a pinching effect of said movable contact members against each fixed contact member to increase the force of engagement of said movable contact members against each fixed contact member incident to heavy current flow, and in which one of said movable contact members engages said fixed contact members before the other and is shaped to create a concentration of the field of electromagnetic force tending to decrease the pressure of said one contact member against said fixed contact members during heavy current flow prior to engagement of said other movable contact member with said fixed contact members.

2. A electric switch as claimed in claim 1 wherein said movable contact members are V-shaped with one inside the other and the outside movable contact is longer than the inside movable contact for engagement of the fixed contact members prior to engagement by the inside movable contact.

3. An electric switch as claimed in claim 2 having means biasing each of said movable contact members individually toward said fixed contact members in contact-engaged position.

4. An electric switch as claimed in claim 1 having means biasing said movable contact members toward said fixed contact members in contact-engaged position.

5. An electric switch as claimed in claim 1 wherein said movable contact members are U-shaped with one inside the other and interengaging means are provided between the transverse portions of said movable contact members and said carrier for positioning said contact members in said carrier.

6. An electric switch as claimed in claim 5 having insulating means between said movable contact members maintaining them separated.

7. An electric switch as claimed in claim 1 having insulating means between said movable contact members maintaining them separated.

8. An electric switch comprising an insulating base, a pair of fixed contact member mounted on said base, two pairs of movable contact members engageable with and disengageable from said fixed contact members, an insulating carrier on which said pairs of movable contact members are mounted, said carrier having a unitary block of insulation with opposite faces, each of which has recessed to receive one pair of said movable contact members, means on said carrier insulating one pair of said movable contact members from the other pair, insulating plate means secured over said recessed faces and holding each pair of said movable contact members in its respective recess, each pair of said movable contact members engaging opposite faces of said fixed contact members and the fields of electromagnetic force cooperating to create a pinching effect against each of said fixed contact members when engaged fully, one of said said movable contact members of each pair engaging said fixed contact members before the other and is shaped to create a concentration of the field of electromagnetic force tending to decrease the pressure of said one movable contact member against said fixed contact members during heavy current flow prior to engagement of said other movable contact member with said fixed contact members.

9. A switch as claimed in claim 8 having means biasing each of said movable contact members individually toward said fixed contact members in contact-engaged position.

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