US3364324A - Multiple main and auxiliary contact arrangement for high-power switch - Google Patents

Description

3,364,324 ENT Jan. 16, 1968 G. PASI UXIIJIARY CONTACT ARRANGEM MULTIPLE MAIN AND A FOR HIGH-POWER SWITCH 2 Sheets-$heet 1 Filed April 6, 1965 INVENTOR Attorney Guido Rasi Jan. 16, 1968 G. PAS! MULTIPLE MAIN AND AUXILIARY CONTACT ARRANGEMENT Filed April 6, 1965 FOR HIGH-POWER SWITCH Sheets-Sheet 2 Guido Pas!" INVENTOR g R1158 1 CM r Attorney United States Patent 3,364,324 MULTHPLE MAIN AND AUXILIARY CONTACT ARRANGEMENT FOR HIGH-POWER SWITCH Guido Pasi, Mantova, Italy, assignor to Montecatini Edison S.p.A., Milan, Italy Filed Apr. 6, 1965, Ser. No. 445,992 Claims priority, application Italy, Apr. 14, 1964, 8,136/64 7 Claims. (Cl. 200146) ABSTRACT OF THE DESCLQSURE A switch assembly for high current-carrying electrical circuitry, especially the switching of electrolytic cells wherein an actuating rod bears via individual compression springs on an array of mutually parallel contact fingers supported at one end by laminated-leaf conductors and carrying a respective working contact and a respective auxiliary contact. The auxiliary contacts of the individual fingers engage spring-loaded plunger-type auxiliary contacts of a stationary contact member while the working contacts co-operate with the stationary working-contact bar. The plungers are connected by conductors in parallel to the working contact of the stationary member while the connecting rod is actuated by an eccentric movable through dead center whereby the compression spring facilitate open-circuiting of the device.

The present invention relates to a multi-contact switch for switching on and off electrical apparatus working at very high operational power ratings, for example for the short-circuiting of electrolytic cells for the production of chlorine and caustic soda.

It is well known that when conventional switches for electrolytic cells are opened or closed they are under heavy stress because of the very high potential power present on the surfaces of the contacts. Thus, localized melting with the consequent formation of nodules or bridges on the contact surfaces inevitably occurs, thereby causing deterioration of the contacts; furthermore, each surface irregularity results in the removal of the thin silver layer that commonly covers the contacts and leads to the formation of oxides on the copper surfaces thus bared, thereby considerably increasing the power dissipated at the contacts.

Furthermore, the presently known switches for electrolytic cells involve serious difiiculties of cleaning, inspection, etc., due to their particular positioning and construction characteristics.

It is an object of this invention to provide a switch for electrolytic cells for chlorine and soda, which eliminates the drawbacks of the conventional switches by allowing, above all, a substantial reduction of the voltage drop across the contacts (and therefore keeping the heating of the contacts at a minimum), facilitation of maintenance, reduction of the tendency toward localized melting, and assurance of optimal contact pressures.

A further object of this invention is that of providing a switch with a plurality of contacts connected in parallel among themselves, a part of these contacts having an auxiliary function and being easily replaceable when worn out.

3,364,324 Patented Jan. 16, 1968 Still another object is that of providing a switch in which at least the operating contacts are assured of long operational life.

The invention resides in a multiple-contact switch for electrical equipment working under very high operational power ratings, which switch comprises two contact-carrying plates, of which one is stationary and the other is movable and supported by a flexible conductor; the contact-carrying plates are provided with two series of contacts connected to each other in parallel, one series forming the working contacts and the other series being auxiliary or butler contacts, which latter are of easy replacement. The movable plate is operated for the fast closing and opening of the two series of contacts, by a control device including a connecting rod having a free end coupled to the movable plate through compression springs.

The invention will now be described by way of example with reference to the accompanying drawing, wherein:

FIGURE 1 is a side view, partly in section, of a switch embodying the invention, connected to the input terminals of a cell; and

FIGURE 2 is a perspective view of a switch similar to that shown in FIGURE 1 but with a variant in the fixed contact-carrying plate.

The switch shown consists essentially of a first series of working contacts, of a second series of auxiliary or buffer contacts connected in parallel with the first series, and of a control system for the closing and opening of the contacts.

FIGURE 1 shows one pole 1 of an electrolytic cell (not shown) to which a sturdy straight copper bar 3 is rigidly fastened by bolts 2. Connected to bar 3 is a fixed contact 4 consisting of a straight bar on which is welded a strip of silver 4' to reduce contact resistance and achieve minimum voltage drop.

FIGURE 2 shows a modification in which pole 1 is replaced by two overlapping bars 1, 1 to increase the current-carrying capacity of the terminal. Copper bar 3 is made substantially S-shaped and fixed contact 4 is a separate L-shaped bar or plate, bolts 2 being used to fasten bar 3 and contact 4 to bars 1', 1".

In each of these arrangements contact 4 is arranged to make contact with a series of movable contacts 5 mounted, as described below, on a movable plate, and each provided as a layer or strip of silver. Contacts 4 and 5 form working contacts of very long operational life.

On the free end of fixed plate 3 a series of movable contacts a, 6', 6" etc. (see FIGURE 2) is mounted, opposite which are mounted on the movable plate a corresponding number of contacts '7, 7', 7" etc. meant to serve as buffer contacts (i.e. easily replaceable auxiliary contacts) which are designed to contact the corresponding mobile contacts 6, 6', 6 etc. before the working or primary contacts 4 and 5 close.

The mobile contacts 6, 6', 6" etc. are formed by small piston-like bolts 8, passing through holes in the fixed plate 3 and electrically insulated from the support by means of insulating sleeves and washers so as to avoid sticking of the piston rods 8 in their corresponding holes because of volatic arcs during the opening and closing of the contacts.

On each piston 8, between contact 6 and plate 3, a pressure spring 9 is provided to bring contacts 6 back to their rest positions when the contacts 6 and 7 are opened. The electrical connection between fixed plate 3 and the various mobile contacts 6, 6, 6" etc. is by means of flexible conductors 1t 1t), 10" etc.

During closing, the mobile contacts 6 are pushed upwards by the fixed contacts 7 thereby loading the corresponding springs 9 and ensuring good contact, thus allowing the immediately subsequent closing of the working contacts.

The movable contact-carrying plate consists of a series of copper bars (or contactfingers) 11, 11', 11" etc., mounted close to each other in the same plane and each connected by bolts 12 to a flexible conductor 13 which in turn is connected to the other pole 14 of the electrolytic cell by means of bolts 15 and 16. Each copper bar 11, 11, 11", etc., carries a working contact and a butler contact (or auxiliary contact) 7. Each contact 5 is formed by silver strips same as the corresponding fixed contacts 4. The use of several copper bars forming a movable contactcarrying plate ensures a greater number of contact points than the use of a single copper plate.

The flexible conductor 13 consists of a pack of copper laminae which are bent at 90 and welded to each other at their ends so that the flexible part of the pack is limited to the curved section in order to allow the copper bars 11, 11, 11" etc. (with contacts 5 and 7) to oscillate in the direction of the longitudinal axis without allowing any lateral movements. On the side to which are fixed the copper bars 11, 11, 11" etc. slots 17, 17' etc. (see FIGURE 2) have been milled along the whole curved section of the pack of copper laminae 13 to render the various copper bars 11, 11', 11", etc. independent of each other.

When the fixing bolts 15 and 16 are loosened, the flexible conductor 13 can slide along its own axis thereby allowing adjustment of the position of the movable working contacts with respect to the fixed contacts.

The closing and opening control system of the contacts is formed by a support or bracket which carries a driving shaft 19 to which is attached a control lever 20 connected, through tie-bars not shown in the drawing, to a main shaft which is manually controlled. On shaft 19 is fixed a crank 21 on which is pivoted the large end of a control connecting rod 22. The stem of the connecting rod 22 is divided into two parts having their adjacent ends one threaded clockwise and the other counter-clockwise they are held together by a correspondingly threaded sleeve 23, so that by turning sleeve 23 it is possible to vary the effective length of the connecting rod in the manner of a turnbuckle; this serves to adjust the contact pressure, and for maintenance and servicing the contacts may be moved apart for cleaning or replacing. The small end of connecting rod 22 consists of a fiat bar or yoke 24 on which are mounted as many small guiding cylinders 25, 25' etc. as there are movable working contacts 5 (or copper bars 11, 11', 11", etc.), on each of which are disposed pressure springs 26 and pistons 27 I whose conical top partially penetrates into the body of the copper bars (or contact fingers) 11, 11', 11 etc.

An aligning member 28 is provided to keep the contact fingers 11, 11, 11", etc. aligned with each other and to cause the contacts to part in the opening operation.

The switch hereinabove described works in the following way; for closing the contacts it is enough to shift lever 20 from position 20' (see FIGURE 1) into position 20 whereby the shaft 19 and crank 21 are rotated. To connecting rod 22 is thus imparted an upward motion by which the contact fingers 11 are pushed forward against the contacts mounted on the fixed plate 3.

The device is adjusted in such a way that the auxiliary or butter contacts 6 and 7 close first and then are followed by the working contacts 4 and 5, while the connecting rod,

continuing with its upward motion, loads the pressure springs 26 and ends its movement at its top dead centre (see FIGURE 1). The stroke of the contact fingers and the pressure of the springs 26 are regulated by adjustment of sleeve 23. The contacts are opened by turning the shift lever 20 in the opposite direction. When the connecting rod 22. has left top dead center the opening takes place independently of the operational speed of the operator, since the opening speed depends on the energy discharged by the springs 26. Contrary to what happens during closing the working contacts 4 and 5 open first and the auxiliary or buffer contacts 6 and 7 then open.

What I claim is:

1. A high current-carrying capacity switch assembly for electrical circuitry, comprising a stationary contactcarry member and a movable contact-carrying member juxtaposed with and shiftable toward and away from said stationary contact-carrying member; a set of pairs of juxtaposed co-operating auxiliary contacts spaced along said members and replaceable thereon; a set of co-operating working contacts extending along said members and mutually engageable upon displacement of said movable member toward said stationary member subsequently to the mutual engagement of said auxiliary contacts, said movable contact-carrying member being formed by a plurality of mutually parallel individually shiftable conductive contact fingers each carrying a respective auxiliary contact of one of said pairs, the other of said auxiliary contacts being mounted on said stationary member and being electrically connected in parallel with one another, each of said fingers carrying also a respective working contact of said set, the corresponding working contact being mounted on said stationary member; and actuating means including a rod extending transversely of said members acting upon said movable member, and compressionspring means associated with said conductive fingers and stressable by said rod to shift said fingers relatively to said stationary member.

2. A switch assembly as defined in claim 1 wherein said compression-spring means includes a support plate extending generally parallel to said members and provided with an array of compression springs each bearing upon a respective one of said fingers.

3. A switch assembly as defined in claim 2, further comprising an aligning bar extending along said contact fingers transversely thereof and engageable with a side of said contact fingers opposite that along which said support plate is disposed, and means connecting said bar with said support plate for joint movement of said bar and said support plate with said rod in switch-opening direction to entrain said fingers away from said stationary member.

4. A switch assembly as defined in claim 2, further comprising conductor means connected with said moveable contact-carrying member and including a plurality of flexible conductors of stacked-laminate construction bent at about a right angle and alfixed to said fingers said 1 conductors being separated by slots milled through the thickness of the stacked-laminate construction, the lamellae of said conductors being rigidly connected at spaced locations on opposite sides of their right-angle bends to prevent lateral shifting of said fingers.

5. A switch assembly as defined in claim 4 wherein each of said fingers is formed with a recess aligned with the respective springs and said compression-spring means includes a respective conically tipped pin axially engaged by the respective spring and projected into the resepective recess, and a respective sleeve surrounding each spring and the respective pin.

6. A switch assembly as defined in claim 4 wherein said other auxiliary contacts are formed as plungers slidably received in said stationary contact-carrying member and are shiftable in the direction of movement of said 5 6 fingers, said assembly further comprising compression References Cited springs bearing upon said plungers to counteract the U IT STATES PA EN S displacement thereof in switch-closing direction, and con- 2,302 394 11/1942 Seaman ductor means individual to said plungers electrically connecting same with the working contact of said stationary FOREIGN PATENTS contact-carrying membe 177,827 3/1954- Austria.

7. A switch assembly as defined in claim 4, further 1,016,799 10/1957 Germanycomprising adjustment means on said rod for varying the 1145698 3/1963 yeifective length thereof. 10 ROBERT S. MACON, Primary Examiner.

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