US2261845A - Switch - Google Patents

Description

Nov. 4, 1941. F. s. DENNEEN ET AL SWITCH Filed Nov. 15, 1937 2 Sheets-Sheet 1 Nov. 4, 1941. F. s. DENNEEN ET AL SWITCH 2 Sheets-Sheet 2 Filed Nov. 15, 1937 INVENTORS.

Patented ,Nov. 4, 1941 2,261,845 SWITCH Francis S. Denneen, Cleveland, and William C.

Dunn, Shaker Heights, Ohio, assignors to The Ohio Crankshaft Company, Cleveland, Ohio, a

corporation of Ohio Application November 15, 1937, Serial No. 174,611

8 Claims.

This invention relates to apparatus for establishing electrical connection between two conductors and more particularly to mechanism in which the contact is established by pressure operating means.

Heretofore in connecting two conductors handling comparatively heavy currents, particularly high frequency currents, the heat developed in the switch was so great as to require a large and cumbersome switch mechanism, which was not only expensive to construct but to maintain.

Such switches have heretofore not been mounted directly on the bus bars or other conductors for which they control the delivery of current, and the advantageof such switches has not been brought to the attention of those skilled in the art prior to the present teachings.

The chief object of our invention therefore has been to provide a simple field switch of novel and simple construction and capable of iming supported directly on a bus bar or conductor and to provide means for the operation of such a switch thus supported.

Other and related objects of our invention are as follows:

To provide a light, compact switch capable of efliciently handling current of high amperage;

To provide a switch, one contact face of which is directly attached to a bus bar;

To provide a. switch capable of quick removal and replacement of the main unit and of the principal individual parts;

To provide a practical switch capable of continuously operating under high pressure values when applied to the contacting faces;

To provide a switch capable of supporting the weight of heavy conductors attached to a moving contact member of the switch;

To provide a practical switch capable of operating continuously regardless of the corrosion or oxidation of the contacting faces;

To provide a switch capable of operating under high or low pressure between the contacting surfaces. v

To provide a substantially direct path switch mechanism particularly suited to the handling of high frequency currents;

To provide a switch having the above named advantages and capable of remote control;

To provide a switch with contacting faces compressible under pressure and arranged for the self alignment of the contacting faces when under pressure.

To provide a remote control switch operating under fluid pressure;

To provide a switch that introduces minimum added impedence to the circuit;

Other objects will become apparent from an examination of the drawings which illustrate certain forms of our invention and from the description in the following specification which reswitch fers to the said drawings. The novel features are summarized in the claims.

In the attached drawings:

Fig. 1 is a side elevation of our improved Fig. 2 is an end elevation partly in section further illustrating the switch construction;

Fig. 3 is a fragmentary section as indicated by the lines 3-4 on Fig. 1;

Fig. 4 is a fragmentary view showing a detail of the contact faces;

Fig. 5 is a diagram showing the relative positions of the conductors comprising a circuit controlled by our improved switch;

. Fig. 6 is a fragmentary section similar to Fig. 1, but showing a, modification of the improved switch;

Fig. 7 is a fragmentary section substantially on line '|--'l of Fig. 6, and

Fig. 8 is a central section through Fig. 1 in a plane parallel to Fig. 1.

As indicated above, the switch serves as means for connecting heavy conductors, usually in the form of cables, directly to bus bars supplying current of high density and often of high frequency. A multiplicity of cables is usually employed as a conductor to eliminate self inductance of a single cable and because several cables are more flexible andmore easily handled than a single large cable. Further, when high frequency currents are employed, several cables are readily held or bound together in close parallel relationship so that the inductive effect of one opposes the inductive effect of another, thus greatly reducing the power lost by inductive ef- In the preferred form, which is shown in Figs. 1-4, the switch comprises the insulating support l0, usually made of micarta or of some other insulating material possessing good mechanical strength. This support is securely held between the bus bars II and I2 by bolts Hi, the latter being provided with suitable insulating bushings H with flanges or washers. At its top the support carries a bracket which has bearing bosses at the ends of its oppositely extending arms for receiving oscillating bolts [6 and spacers IT. The spacer H is somewhat longer than the boss of bracket l5 and serves as means for locating arms i8 and IS in firm and spaced relationship when the nut of bolt I6 is tightened. The two arms [8 and I9 and the bolt l5 and spacer I 1 thus form a substantially rigid unit having the spacer rotatable in the boss of bracket 15.

Secured between the lower ends of arms l9 and I9 by bolts or rivets are carriers 2| for the oscillating supports 22. These supports carry blocks 23 and 24. The blocks serve as terminals for the groups 25 and 23 of the aforementioned cables which it is desired to connect to the bus bars. These blocks are usually rectangular pieces of copper with a series of drilled and counterbored holes for the cable ends. The insulation is removed from these cable ends as shown in Fig. 3 and the exposed metal of the cable is inserted in the lower ends of the drilled holes. The space around the exposed metal of the cable, provided by the counterboring, is filled with a fusible metal, as solder, which secures each cable in good current conducting contact with the metal of the block. The insulation being cut away as at 21, provides a shoulder which bears against the lower face of the block and thus limits the amount the bared metal of the cable can be inserted in the drilled recess. After soldering the cable ends in place the solder is removed from the upper part of the blocks to present smooth flat surfaces for attaching supports 22 which are held thereon by studs 28 and are insulated from the blocks by insulators 29 and 30.

The oscillating supports 22 have spindles which enter bores provided therefor in the carriers 2|. These spindles have a limited oscillating movement in the bores which permits blocks 23 and 24 to adjust themselves to parallelism with the bus bars and thus insure contact along the entire width of the contact faces. The pins or screws 32 hold the spindles against longitudinal movement while the elongated openings in the carriers 2! which receive the protruding ends of these pins, permit the oscillating movement required for the above adjustment to parallelism.

Copper to copper contacts between the conductor blocks and the bus bars are objectionable because copper oxidizes readily and the oxide offers resistance to flow of current. We avoid this trouble by attaching to each bus bar and to each contactor block a strip of silver, preferably coin silver, as indicated at 33 and 34. The contact is thus made between silver surfaces which, under pressure, have fairly high conductivity and whose oxides are recognized as favorable conductors.

To avoid the extreme accuracy of construction required to bring a flat surface of the strip of silver on the block into uniform engagement with a corresponding flat surface on the bus bar one or both of the silver strips are somewhat curved, as best shown in Fig. 4. The radius of curvature being large and the silver being relatively soft, the curved surface of one strip somewhat imbeds itself into the surface of the other strip thus automatically providing an adequate area of contact.

An air chamber is employed to oscillate the two pairs of arms about the centers of bolts IE to move the blocks 24 and 23 toward the bus bars, and thus to establish the contacts as above described. This is best shown in Figs. 1 and 8. This chamber in itself is of well known construction having a flexible rubber diaphragm 33 securely clamped between a housing 31 and a cover 33. Attached to the diaphragm near its center is a plunger or rod 39 which passes out through a central opening of the housing. A

bellows like covering 40 surrounds the rod 39 and is attached to the housing to exclude foreign matter from the said housing. The housing of this air chamber is attached to bracket 4| which is of correct width to fill the space between the members of one pair of arms. Bolts 42 pass through the arms and enter the bracket 4| thu providing bearings for the oscillation relative to the arms of the bracket and its attached air chamber. The rod or plunger 39 is attached to a T-shaped member 4! which extends between the members of the other pair of arms. The bolt 43 and a suitable tubular spacer holds the ends of these arms firmly in correct relative position, the tubular spacer serving as a bearing surface for a bore in the T-shaped member and thus permitting oscillation of this member relative to its associated pair of arms.

A helical spring 31 surrounding the rod or plunger 39 within the housing normally holds the diaphragm 35 adjacentto or in contact with the interior or the cover 33. The rod 39 attached to this diaphragm is thus held by the spring in its maximum retracted position, bringing the upper ends of the opposite pairs of arms in their closest position, thus maintaining the bloclm well spaced from the bus bars.

When air under suitable pressure is admitted to the air chamber through pipe 44 by a valve controlling the flow, the diaphragm is flexed, the release spring within the housing is compressed and plunger 39 is forced outward from the housing. This movement of the plunger rocks the pairs of arms on their centers, moving the blocks toward respective bus bars, and brings the silver strips on the blocks into firm pressure engagement with the strips on the bus bars. This establishes a highly efficient electrical contact for conducting current to the groups of cables 25 and 26.

When the air is cut olf and the pressure within the chamber is suddenly released by a suitable valve the spring in the chamber quickly returns the diaphragm and retracts the plunger 39 breaking the contacts of the bus bars. An external tension spring, shown at 45, may be employed to supplement the spring within the air chamber to insure complete and sudden opening of the contacts.

To equalize the spacings between the contactors and the bus bars when the switch is in its open position an adjustable stop is provided for each pair of arms. This stop comprises a member 45 attached to each pair of arms, each of these members having an adjustable screw 4'! engaging 9. lug 48 on bracket l5. The opening movement of each contactor may thus be limited and the spaces between contacts equalized.

For the purpose of closing or opening an additional circuit substantially simultaneously with the operation of the contactor blocks 25 and 26, an auxiliary switch is provided. This switch is attached to the inner face of the plate 49. Suitable wires or cables leading to and from this switch pass through an opening 5|. A rod or plunger 52 having a spring return means passes through a wall of the housing 50 and is engaged by an adjustable screw carried by a bracket 53.

This bracket is attached to and is movable with one pair of the operating arms.

The conductors leading to and from the main contacts are usually arranged as indicated diagrammatically in Fig. 5. The conductors 66 and 51 connecting the high frequency supply generator 68 to the bus bars I I and i2 are supported in close parallel relationship; also the conductors 69 and 66, represented by the groups of cables 25 and 26 in Figs. 1 and 2, are brought into as close proximity with each other as is practicable. This close parallel relationship of conductors carrying current of opposite direction greatly reduces the inductive effect and the loss of power due to heat generated in adjacent current conducting articles. The bus bars H and i2 themselves being spaced as closely as the mechanical strength of the supporting insulating spacer III will permit, further reduces inductance which would otherwise exist in the circuit.

Frequently switches of this character are required to open circuits carrying currents of high density and under such conditions harmful arcs tend to form at the main contacts burning away the silver and very soon render the device inoperative even when made of parts having very liberal proportions.

To this end the modification shown in Figs. 6 and '7 or its equivalent is used. In this embodiment two contacts are provided. The main contact which is adapted to break first in opening the switch usually has silver surfaces and a second contact, which opens after the main contacts have separated, has considerable resistance,

both ohmic and inductive, and ordinarily has carbon contacting surfaces.

As illustrated, the bus bars 6| and 62 are held in spaced relationship by the insulating member 63 which supports bracket 64, the latter serving as means for carrying mechanism to move the contacting conductors into engagement with the bus bars. Each of the contactor conductors comprises two members. The lower member 65, which has a curved silver strip 66 attached thereto to contact with a corresponding strip 61 attached to the bus bar 62, is supported by, but insulatedly separated from the upper contactor member 66 excepting as current is permitted to flow through coil 69. The lower contactor member 65 serves as means for carrying the cables 10 which correspond to the group of cables 26 of Fig. '1. The upper contactor member 66, which is separated from the member 65 by insulation H, carries the secondary contactor 12 which is urged outwardly by a spring 13 and into engagement with the contact element 14 secured to a part of the bus bar 62. The contactor 12 is limited inmovement by the enlarged part 15 and an insulating seat 16 for the spring prevents current from flowing in this spring. The respective upper contactor members 66 are insulatedly carried by the support 11 which corresponds to support 22 of Fig. 1 and are pivotally supported by "a by the bracket 64.

An expansible mechanism similar to that of Figs. 1 and 8 comprising a plunger and a fluid operated diaphragm is connected between respective arms 11. The mechanism is oppositely connected inthe sense that spring 31' is here a tension spring normally acting to exert a pull rather than push on the parts because in the device of Fig. 6 the fluid mechanism is on the same side of pivots 'I'Ia as the contactors. Similarly, the pipe 44 leads to the opposite side of the diaphragm than in Fig. 1. Thus the arms are retained in position by the application of fluid pressure and on release the corresponding springs disengage the arms.

The primary purpose of this modification being to prevent or to reduce to harmless proportions arcs which tend to form upon breaking contact with the bus bar. means is provided for not only reducing the current flowing at the time the circuit is fully opened, but means is provided to extinguish such are as may form. To this end the coil 69 is-provided to induce a heavy magnetic flux in the core I6 which directs a heavy magnetic field into the region of the contact between members 12 and 14. This field repels the arc upwardly and away from the contacting surfaces of these contacting members. To further supplement the action of this arc, a blast of a cold fluid is projected from the nozzle 19 into the space between the contacting members. The flow of this fluid is automatically provided by a connecting member such as rod 86 which is attached at its one end to a member 8! insulatedly connected to move with contactor 65 and at its other end to a member 62 operating a valve 63 which controls the flow of fluid to the nozzle 19.

When it is desired to interrupt a flow of current from the bus bar 62 to conductors 16 the fluid pressure establishing the current flow is released and supporting members 11 are drawn by the spring away from the respective bus bars. The first part of this movement opens the contact between the silver strips at 66 and 61 through which the greater part of the current has been flowing. The contact between members l2 and 14, being maintained by virtue of spring 13, causes the current formerly flowing through contacts 66 and 61 to be diverted to the contacts I2 and 14. As contacts I2 and 14 have a relatively high resistance, but considerably less than the air gap formed at 66 and 61 theformer current in greatly reduced proportions will flow through the contacts 12 and I4, preventing more than a very small amount of arcing at the silver contacts and leaving only a small amount of the original current to be interrupted when contacts 12 and 14 separate, which occurs upon a continued movement of the members 65 and 68, these contacts being in engagement until the enlarged part 15 of contactor 12 engages the bottom of its recess in member 68.

Upon the breaking of contacts 66 and 61 all current passing through contacts 12 and 14 from the bus bar 62 to cables 10 flows through coil 69, causing flux of relatively high density to permeate core 18 and thus direct a repelling field in the region of contact of members 12 and 14. As the movement of members 65 and 68 continues, rod 86 through arm 82, opens valve 83 to deliver a heavy blast of air or other fluid into the region of contact of members 12 and 14. Thus at the instant this latter contact is broken the combined effect of the repelling magnetic field and the cooling of the fluid blast extinguishes almost instantaneously such are as may be formed by the rupture of the reduced current flowing through the contact members 12 and 14.

It will be understood that we may employ a series of several pairs of contact members such as 12 and 14, the several pairs opening successively and each successive pair carrying less current than its predecessor so that not only will the current flowing through the last pair be very small but the difference in the next pair to open will be so small that no perceptible arc will occur at these main contacts.

The current transmitted by the present switch is usually of high density and heating frequently occurs, especially when the switch is opened and closed in rapid succession or is used for current of high frequency. This latter is the type of service for which this switch is particularly adapted and hence cooling means is often needed and usually when space limitations require that the elements of the switch be made in limited proportions. This cooling is accomplished by recessing over considerable areas the sides of the supporting insulating plate 83 as is shown at N and 85. Connections for the inlet of cooling fluid are provided as at 86 and 81 and the cooling fluid, after circulating through these spaces, is discharged through piping 86' and II. The contacting member 85 is also readily cooled by connecting sources of cooling fluid as at ll.

It will be seen from the foregoing description that we have provided a novel and improved switch for the handling of heavy currents with a minimum of equipment. It will be seen that the apparatus is particularly adapted to the handling of high frequency current and effects the making or breaking of a connection at each lead simultaneously.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In switch apparatus of the class described, a flat frame, a bus bar conductor secured to each face thereof and insulated from the other, a pair of members pivotally carried by said frame and shiftable in a plane perpendicular'to the plane of said faces, a contact block secured to each member, a flexible conductor fastened to each contact block, a pad on respective bus bars and contact blocks to establish electrical connection tween a bush bar and a respective conductor, a fluid expansible means secured at each end to one of said members, a source of fluid for said expansible means and operative to pivot said members and make and break contact between said pads.

2. In switch apparatus of the class described, a supporting frame, a pair of current conductors carried therewith and insulated from each other, a pair of members pivotaily carried by said frame and shiftable toward and away from a respective conductor, a terminal block carried by each member and insulated therefrom and adapted to engage a respective conductor, a lead to said respective block independent of said member, a fluid expansible means secured at each end to one of said members and operative to pivot said members and make and break contact between said conductors and terminal blocks.

3. In apparatus of the class described, a conductor support, a pair of conductors carried therewith, a bracket extending outwardly from said support, a pair of arms pivotaily carried by said bracket and movable toward and away from said conductors, a terminal block carried by each arm and insulated therefrom, a current conducting member connected to each block and mechanism interconnecting said arms and comprising a fluid-operated plunger and a chamber therefor carried by respective arms and operative to shift said terminal blocks with respect to said respective conductors.

4. In apparatus of the class described, a base, a pair of conductors carried therewith, an arm supported by said base, two contact points insulated from each other and carried by said am and adapted to engage one of said conductors, means to shift said arm and engage said points against said conductor, and means operative on movement of said arm away from said conductor to initiate a blow-out directed at the region of contact between one of said points and said conductor to decrease the arcing effect, said lastnamed means comprising a coil connecting said two points.

5. In switch apparatus of the class described, a supporting frame, a pair of circuit conductors carried thereby and insulated from each other, a pair of members shiftably carried by said frame and movable toward and away from a respective conductor, a contacting face integral with each member and adapted to engage a respective conductor, a lead to each of said contact faces and a fluid expansible means secured at one end to one of said members and at the other end to the other of said members and operative to shift said members and make and break contact between said conductors and said faces.

6. In switch apparatus of the class described, a frame, a pair of bus bar conductors carried by said frame and extending in the same direction, a contact face formed on each conductor, a pair of members shiftably carried by said frame in a direction to and from the said contact faces, a contact face formed on each member and adapted to engage a respective face on each conductor, a fluid expansible means secured at each end to one of said members and operative to shift said members and make and break contact between said members and their respective faces, and a source of fluid for said expansible means.

7. In apparatus of the class described, a support, two conductors carried therewith, a pair of arms carried by said support, each of said arms being movable toward and away from said conductors, a contact carried by each of said arms, the contacts on each of said arms adapted to respectively engage one of said two conductors, and mechanism comprising a chamber connected to one of said arms and a fluid operated plunger therein connected to the other of said arms and operative to shift said arms with respect to their respective said conductors.

8. In apparatus of the class described, a base, a pair of conductors carried thereby, a pair of arms each movably carried thereby and adapted for respectively engaging said conductors, means interconnecting said arms for actuating the same, and means limiting the movement of one of said arms away from its respective conductor whereby further actuation of said first-named means actuates solely the other of said arms.

FRANCIS S. DENNEEN. WILLIAM C. DUNN.

Images