US3238339A

US3238339A - Heavy duty switch held in closed position by parallel current branches and assisted in movement to open position by antiparallel branches

Info

Publication number: US3238339A
Application number: US179052A
Authority: US
Inventors: Fehling Heinz
Original assignee: Licentia Patent Verwaltungs GmbH
Current assignee: Licentia Patent Verwaltungs GmbH
Priority date: 1961-03-13
Filing date: 1962-03-12
Publication date: 1966-03-01
Anticipated expiration: 1983-03-01
Also published as: DE1161350B

Description

March 1, 1966 H. FEHLING 3,238,339

HEAVY DUTY SWITCH HELD IN CLOSED POSITION BY PARAL CURRENT BRANCHE S AND ASSISTED IN MOVEMENT TO OPEN PO TION BY ANTIPARALLE L BRANCHES Filed March 12, 1962 I Hm: Icwn Qttovnag Jnvenfor:

United States Patent O 3,238,339 HEAVY DUTY SWITCH HELD IN CLOSED POSI- TION BY PARALLEL CURRENT BRANCHES AND ASSISTED IN MOVEMENT TO OPEN P051- TION BY ANTIPARALLEL BRANCHES Heinz Fehling, Mecklenburger Weg, Einfeld, near Neumunster, Germany, assignor to Licentia Patent-VerwaItungs-G.m.b.H., Frankfurt am Main, Germany Filed Mar. 12, 1962, Ser. No. 179,052 Claims priority, application Germany, Mar. 13, 1961, L 38,422 7 Claims. (Cl. 200-146) tThe present invention relates to the electric switching ar More particularly, the present invention relates to a heavy duty switch which is capable of handling large amounts of currents and which will open when the current reaches a given rated current, i.e., a heavy duty circuit breaker having current-limiting characteristics. Switches of this type require contact elements in which the current communication from the main contact portion to the contact portion at which the arc is ignited occurs satisfactorily, even when the current is interrupted at high speed. It is particularly important that the main contact portions will mot be damaged during switch opening. Such damage can be caused as the result of short-circuit current pulses having a high peak value, or as the result of the electrodynamic forces within the portions of high current density of the points of engagement of the contact elements, or as the result of current loops formed by the current leads connected to the contact elements.

Recently, current-limiting circuit breakers have been developed in which electrodynamic and magnetic forces produced by the short-circuit current are used for opening the contact system. If such circuit breakers are used as overload switches for protecting a motor which is difficult to start, then the switch should not open until the short-circuit current is more than eight to sixteen times the rated current of the switch; until such current value has been reached, the switch must remain insensitive to the electrodynamic forces.

It is, therefore, an object of the present invention to provide a switch which is able to fulfill the above requirements, and, with this object in view, the present invention resides mainly in a switch which comprises movable and stationary contact members provided with contacts that serve to conduct current when the switch is closed, as well as with arching contacts which carry the current just prior to the time the switch assumes its open position. According to the instant invention, the arrangement of the contacts is such that, so long as the switch is closed, the current through the two contact members will flow in parallel current branches, thereby creating electrodynamic forces tending to maintain the switch in closed position, whereas when the switch has moved from its closed position to an intermediate position, the current through the two contact members will flow in antiparallel current branches which create electrodynamic forces tending to urge the switch into the open position. More particularly, each contact member has sequentially arranged and spaced-apart main, intermediate and arcing contacts which cooperate with respective sequentially arranged and spaced-apart main, intermediate and arcing contacts of the other contact member. In closed position, the main and intermediate arcing contacts are in engagement with each other, and, as the switch moves into its intermediate position, the intermediate and arcing contacts will at first be in engagement with each other whereafter only the arcing contacts will be in engagement with each other. To assist this move- 3,238,339 Patented Mar. 1, 1966 ment, one of the intermediate contacts is fashioned as a roll-off type contact about which the movable contact member moves, the entire arrangement being, as stated above, such that the current flows in parallel branches while the switch is closed, thereby helping to maintain the switch closed, but in antiparallel branches as the switch is in the process of being opened, thereby helping the opening.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an elevational view of one embodiment of a switch according to the present invention.

FIGURE 1a is a schematic diagram showing the current flow through the switch illustrated in FIGURE 1.

FIGURE 2 is a perspective view of the stationary contact member of the switch of FIGURE 1.

FIGURE 3 is a sectional elevation of a modified embodiment of a switch according to the present invention.

FIGURE 3a is a schematic diagram showing the current flow through the switch illustrated in FIGURE 2.

Referring now to the drawings, FIGURES 1 and 2 show a contact arrangement according to the instant invention which comprises a stationary contact member 1 and a movable contact member 2. The member 1 carries sequentially arranged and spaced-apart first, second and

third contacts

3a, 4a, and 5a, which cooperate with respective sequentially arranged and spaced-apart first, second and

third contacts

3b, 4b, 5b, carried by member 2. In practice, contacts 3b and 4b may simply be different portions of a single contact bridge affixed to the contact member 2. The main contacts 3a, 3b, and the

intermediate contacts

4a, 4b, constitute main contact means whereas the

contacts

5a, 5b, are arcing contacts. The current lead 6 is in the form of a bus bar connected to the contact member 1 at a point closest to the contact 4a, whereas the lead 7, which is flexible so as to allow the contact member 2 to be moved relative to the sta tionary contact member 1, is closest to the contact 3b.

The contact member 2 is movable relative to the stationary contact member 1 from the closed position shown in FIGURE 1, wherein the main and intermediate contacts 3a, 3b; 4a, 4b, are in engagement with each other, through an intermediate position in which at first the

intermediate contacts

4a, 4b, and the arcing

contacts

5a, 5b, are in engagement with each other but after which only the arcing

contacts

5a, 5b, are in engagement with each other, to an open position in which none of the contacts is in engagement with any other and in which the spring-biased roller element 8 will slide off the cam surface 9. In order to allow this type of movement, the contact 4:: is fashioned as a roll-off contact.

The current flow through the contact members is depicted in FIGURE 10. Since the main and intermediate contacts 3a, 3b; 4a, 4b, are closed and the

arcing contacts

5a, 5b, are open, the current coming in via lead 6 and leaving via lead 7 is divided into two parallel current branches or paths. These branches create forces which tend to maintain the movable contact member 2 in its closed position. If the contact arrangement provides for a three-point engagement, as shown in FIGURE 3, the force P which tends to separate the contacts may be obtained by the following, empirically derived equation:

where n=the number of contact points. On the other hand, the force K which tends to urge toward each other two parallel conductors of finite length through which current flows is represented by the following equation:

where L is the length of the two conductors and a the average distance between the conductors. In order to obtain a force which tends to increase contact pressure, K must be larger than P. The equations show that L/a has to equal C 1.5. If there are 11:3 contact points, it is sufficient if the factor C is 1.5 C5, i.e., if the ratio L/a is about 7. According to the present invention, the ratio L/a is so matched to the actuator associated with the switch, i.e., to the current value at which such actuator is actuated, that the switch will remain safely closed until the actuator is energized.

Upon actuation by the electromagnetic actuator, both it and the electrodynamic forces will turn the movable contact about roll-off contact 4a so that contacts 3a, 3b, .are opened and the arcing contacts a, 5b, enter into engagement. As a result, no more current can flow through the parallel current branches. Moreover, as soon as the

contacts

4a, 4b, are separated, the entire current will 'fiow through the current loop via

contacts

5a, 5b. The current in the two branches will now be antiparallel, i.e., parallel but in the opposite direction. The electrodynamic forces are now such that they will assist the movement of the movable contact member 2 from its intermediate position to its open position. The fact that the direction of the cur-rent in the two branches has now been changed will also bring about a self-generated strong magnetic blow-out of the are which will occur at the

contacts

5a, 5b.

In practice, the current may be fed to the arcing

contacts

5a, 5b, either by the bus bar shown in solid lines (FIGURES 1 and 2), or by leads or straps 11, shown in dot-dash lines (FIGURE 1).

The embodiment shown structurally in FIGURE 3 and schematically in FIGURE 3a is similar to the abovedescribed one in that it also includes stationary and movable contact members 1' and 2' carrying

contacts

3a, 3b, 4a, 4b, 5a, and 5b, as well as leads 6 and 7, and the spring-biased roller element 8' and cam 9'. However, the stationary contact member, instead of being a single piece, comprises a first part to which the

contacts

3a and 4a are afiixed and a second part 13 which is pivotally mounted on a pin 12. The part 13, whose rightwardly-directed bulge, as viewed in FIGURE 3, constitutes the arcing contact 5a, is yieldable and is acted upon by a spring 13a carried by a rod 1311 which itself is pivotally connected to the part 13 and passes through a stationary stud 15. A strap 14 is provided for establishing a satisfactory elec trical connection between the part 13 and the lead 6'. The arrangement of the pants is thus such that, when the movable contact member is in its closed position, all of the cooperating contacts, including the arcing

contacts

5a, 5b, are in engagement with each other so that the current through the switch is divided into three pants, there being, as best shown in FIGURE 3a, a parallel current branch as well as an antiparallel current branch.

By properly selecting the contact pressure as well as the correct ratio of the length of the parallel branch to the length of the antiparallel branch, the force which tends to urge the contacts 301, 3b; 4a, 4b, together will not be reduced. Only when the electrodynamic or magnetic tripping actuator is energized will the movable contact member 2 roll off contact 4a and press the part 13 rearvvardly until it abuts the head of the stud 15, the parts then assuming the position shown in dashed lines. The movable contact member is then in its intermediate position and the entire current will flow through the arcing contacts. Consequently, the current wiil flow only in antiparatllel branches and the electrodylnamic forces will urge the contact member 2 toward its open position.

The electromagnetic actuator, Le. a tripping device that is actuated by the current passing the switch, and a trip lever mechanism between the movable contact member and a spring loaded during the switch-in moving of movlable contact member in the switch-in position or looses it according to tripping of the actuator for travelling in the switch-out position may be of conventional form.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A switch comprising an elongated stationary contact member and an elongated movable contact member, each contact member having a means which forms an elongated current conductive path, the two current conductive paths, throughout substantially their entire lengths, being generally parallel to each other and in close proximity to each in consequence of which the two magnetic fields which result firom the flow of current through the respective current conductive paths will affect each other, each contact member carrying, along the lengths of its respective means which forms the elongated current conductive path, sequentially arranged and spaced-apart main, intermediate and arcing contacts which cooperate with respective sequentially arranged and spaced-apart main, intermediate and arcing contacts of the other contact member, a current lead connected to one of said contact members at a point thereon closest to its main contact and another current lead connected to the other of said contact members at a point thereon closest to its intermediate contact, said movable contact member being movable relative to said stationary contact member from a closed position in which at least said main and intermediate contacts are in engagement with each other, thereby causing ciongatted parallel current branches in said conductive paths of said stationary and movable contact members which tend to maintain said movable contact member in its closed position, to an intermediate position in which only said arcing contacts are in engagement with each other, thereby causing elongated antiparallel current branches in said conductive paths of said stationary and movable contact members which tend to move said movable contact member out of its intermediate position toward its open position in which none of said contacts is in engagement with any other.

2. A switch as defined in claim 1, wherein the intermediate contact of one of said contact members is a rolloff type contact about which said movable contact member moves fromits closed position to its intermediate position.

3. A switch as defined in claim 1, wherein said arcing contacts are out of engagement with each other when said movable contact member is in its closed position, whereby when said movable contact member is in its closed position there will be only parallel current branches in said contact members.

4. A switch as defined in claim -1, wherein said arcing contacts are also in engagement with each other when said movable contact member is in its closed position, whereby when said movable contact member is in its closed position, there will be both parallel and antiparalllel current branches in said contact members.

5. A switch as defined in claim 4, wherein said static ary contact member comprises a first part carrying said stationary main and intermediary contacts and a second part which is yieldably mounted on said first part and carries the arcing contact pertaining to said stationary contact member.

6. A switch as defined in claim 1, wherein said main contact of one of said contact members includes at least one contact element forming a bridging contact.

7. A switch comprising an elongated stationary contact member and an elongated movable contact member, each contact member having a means which forms an elongated current conductive path, the two current conductive paths, throughout substantially their entire lengths, being generally parallel to each other and in close proximity to each in consequence of which the two magnetic fields which result from the flow of current through the respective current conductive paths will afiect each other, each contact member carrying, along the length of its respective means which forms the elongated current conductive path, sequentially arranged and spaced-apant first, second and third contacts which cooperate with respective sequentially arranged and spaced-apart first, second and third contacts of the other contact member, said first and second contacts of each contact member constituting a main contact means and said third contact constituting an arcing contact, a current lead connected to one of said contact members at a point thereon closest to its first contact and another current lead connected to the other of said contact members at a point thereon closest to its second contact, said movable contact member being mov able relative to said stationary contact member from a closed position in which at least said first and second contacts of said contact members are engagement with each other, thereby causing elongated parallel current branches said conductive paths of said stationary and movable contact members which create electrodyna-mic forces tending to maintain said movable contact member in its closed position, to an intermediate position in which at first said second and third contacts of said contact members are in engagement with each other but after which only said third contacts are in engagement with each other, thereby causing elongated antiparallel current branches in said conductive paths of said stationary and movable contact members which create electrodynamic forces tending to move said movable contact member out of its intermediate position toward its open position in which none of said contacts is in engagement with any other.

References Cited by the Examiner UNITED STATES PATENTS 2,127,813 8/1938 Graves 200-87 2,849,579 8/1958 Frink 200146 2,959,654 11/1960 CasWell 200-146 KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT K. SCHAEFER, BERNARD A. GILHEANY,

Examiners.

Claims

1. A SWITCH COMPRISING AN ELONGATED STATIONARY CONTACT MEMBER AND AN ELONGATED MOVABLE CONTACT MEMBER, EACH CONTACT MEMBER HAVING A MEANS WHICH FORMS AN ELONGATED CURRENT CONDUCTIVE PATH, THE TWO CURRENT CONDUCTIVE PATHS, THROUGHOUT SUBSTANTIALLY THEIR ENTIRE LENGTHS, BEING GENERALLY PARALLEL TO EACH OTHER AND IN CLOSE PROXIMITY TO EACH IN CONSEQUENCE OF WHICH THE TWO MAGNETIC FIELDS WHICH RESULT FROM THE FLOW OF CURRENT THROUGH THE RESPECTIVE CURRENT CONDUCTIVE PATHS WILL AFFECT EACH OTHER, EACH CONTACT MEMBER CARRYING, ALONG THE LENGTH OF ITS RESPECTIVE MEANS WHICH FORMS THE ELONGATED CURRENT CONDUCTIVE PATHS, SEQUENTIALLY ARRANGED AND SPACED-APART MAIN, INTERMEDIATE AND ARCING CONTACTS WHICH COOPERATE WITH RESPECTIVE SEQUENTIALLY ARRANGED AND SPACED-APART MAIN, INTERMEDIATE AND ARCING CONTACTS OF THE OTHER CONTACT MEMBER, A CURRENT LEAD CONNECTED TO ONE OF SAID CONTACT MEMBERS AT A POINT THEREON CLOSEST TO ITS MAIN CONTACT AND ANOTHER CURRENT LEAD CONNECTED TO THE OTHER OF SAID CONTACT MEMBERS AT A POINT THEREON CLOSEST TO ITS INTERMEDIATE CONTACT, SAID MOVABLE CONTACT MEMBER BEING MOVABLE RELATIVE TO SAID STATIONARY CONTACT MEMBER FROM A CLOSED POSITION IN WHICH AT LEAST SAID MAIN AND INTERMEDIATE CONTACTS ARE IN ENGAGEMENT WITH EACH OTHER, THEREBY CAUSING ELONGATED PARALLEL CURRENT BRANCHES IN SAID CONDUCTIVE PATHS OF SAID STATIONARY AND MOVABLE CONTACT MEMBERS WHICH TEND TO MAINTAIN SAID MOVABLE CONTACT MEMBER IN ITS CLOSED POSITION, TO AN INTERMEDIATE POSITION IN WHICH ONLY SAID ARCING CONTACTS ARE IN ENGAGEMENT WITH EACH OTHER, THEREBY CAUSING ELONGATED ANTIPARALLEL CURRENT BRANCHES IN SAID CONDUCTIVE PATHS OF SAID STATIONARY AND MOVABLE CONTACT MEMBERS WHICH TEND TO MOVE SAID MOVABLE CONTACT MEMBER OUT OF ITS INTERMEDIATE POSITION TOWARD ITS OPEN POSITION IN WHICH NONE OF SAID CONTACTS IS IN ENGAGEMENT WITH ANY ANOTHER.