US 2863016 A
Description (OCR text may contain errors)
L. A. HERCULES SWITCH ASSEMBLIES Dec. 2, 1958 5 Sheets-Sheet 1 Filed March 19, 1956 Dec. 2, 1958 L. A. HERCULES 2,363,016
SWITCH ASSEMBLIES Filed March 19, 1956 5 Sheets-Sheet 2 L A. HERCULES swrrcn ASSEMBLIES Dec. 2, 1958 Fiied March 19, 1956 as m IIlIlIII/IIIIII'IIIIII Dec. 2, 1958 4 1.. A. HERCULES 5 SWITCH ASSEMBLIES Filed March 19, 1956 s Sheets-Sheet 4 Aswan '02 l/Esrae fl/excm 5 rra fmeya 1958 L. A. HERCULES SWITCH ASSEMBLIES 5 Sheets-Sheet 5 Filed March 19, 1956 United States Patent 0 SWITCH ASSEMBLIES Lester A. Hercules, St. Louis, Mo., assignor to Frank Adam Electric Company, St. Louis, Mo., a corporation of Missouri Application March 1a, 1956, Serial No. 572,291
2 Claims. (Cl. 2lltl-67) This invention relates to electric switch gear, and more particularly to quick-make and break fusible switches of the type used in switchboards and panelboards for control of motors, branch circuits and the like.
One of the problems encountered in the design of switchboards is that of reducing the size of the switches, especially the front area so that the switchboard is not excessively wide and high. In general, the dimensions of a switch vary with the rating or power capacity, and where a large number of switches are to be mounted on a switchboard, a compact arrangement is desirable, not only because of the convenience, but because of lessened cost in terms of cabinet, bus bars, and wiring.
A dead front type of construction is required, which means that the switch contacts are operated by exterior switch handles. Often, the switch is provided with associated fuses, and there must be a door affording access to the fuses, the door generally being protected with an interlock so as normally to prevent opening of the door when the switch is closed.
Necessarily, there have been many proposed switch designs. Sometimes, the switch handle is mounted on the side of the enclosure clear of the door, but this arrangement is not suited for switchboard applications, because the handle interferes with compact placement of the switches. In other instances, the switch handle extends through a fixed front panel, clear of the door, but excessive front space must be provided for offsetting the handle from the fuse-access door. Even in those instances where the switch handle has been mounted on the door, the space requirements for the fuses, switch contacts and quick-make and break mechanism have resulted in a rather large assembly. Some savings in front area are possible when the contacts are disposed behind the fuses, but this arrangement introduces difliculties in locating the quick-make and break contact mechanism so that it can be readily operated by the front handle. Strong springs are required to insure proper action, hence the operating linkage must be firmly supported. in the past,
this linkage has usually been mounted on one or both sides of the enclosure.
Accordingly, one of the objects of this invention is to provide a compact fusible quick-make and break switch assembly for switchboards and the like. Among the several other objects of the invention may be noted the provision of an improved switch enclosure; the provision of improved switch-operating and door-interlock mechanism; and the provision of an improved overcentering linkage for insuring quick opennig and closing of the switch.
Briefly, the invention contemplates that the fused switches will be supplied as single or paired units within an enclosure, several such enclosures being mounted on a switchboard or panelboard. The enclosure is in the form of a deep channel open at its ends but for end members adjacent the front thereof. In the twin-unit enclosure, a door is hinged at each end member, and a center bar bridges the front of the enclosure where the doors meet.
The door is provided with an exterior handle. A collar is secured on the handle to bear against the outer face of the door, and a rotary keeper is pivoted on the inner face of the door. The keeper is secured to the collar or handle by screws extending through arcuate slots in the door, and the keeper cooperates with a bolt or lug within the enclosure so as to prevent opening of the door except when the switch handle is in certain predetermined positions.
The door also carries operating mechanism adapted to engage with the operating arm of a switch. This operating arm extends forwardly from the switch and is journalled at the back thereof for rotation about an axis normal to the front of the enclosure. When the door is closed, the end of the switch arm is received within a door-mounted socket and is rotatably held by a doormounted stud, both the socket and stud disengaging from the switch arm when the door is swung open. The socket is then coupled for rotation with the handle and keeper,
so that manipulation of the handle rotates the switch arm.
The switch unit comprises a back panel on which the switch arm is also journalled. An insulated base mounted on the back panel carries fixed switch contacts, and fuse clips may also be mounted on the front of the base for convenient access through the door opening. The base is also provided with one or more branch-circuit terminals at its outer end (adjacent the open end of the enclosure) and a set of bus terminals at its other or inner end. Plug-on bus connectors project from the back of the enclosure for connection with the bus bars of the switchboard or panelboard. It may be noted that the switch unit is relatively permanently fastened in the enclosure, but the enclosure is readily removable from a switchboard or panelboard.
The quick-make and break mechanism for the switch contacts is mounted on the back panel, there being a crank driven by the switch arm and a pair of overcentering links or plates, one of which is adapted to shift a movable contact into and out of engagement with associated fixed contacts. More particularly, the switch arm is a bar extending through the back panel with its end bent over and pivoted on a back surface thereof, so as to form the crank. One of the overcentering plates is pivoted on the same axis, for driven cooperation with the crank. The movable contact or contacts are carried on a plate slidably guided on the front surface of the panel, and a stud extends from the contact plate through a slot in the back panel. This stud is then engaged within a somewhat larger opening in the overcentering plate, the arrangement being one that affords lost motion and develops increasedleverage as the movable contact approaches the fixed contacts. The second link of the overcentering linkage is a plate pivoted adjacent the crank for movement therewith in a direction opposite to that of the first link. Both links have limit stops, and a spring is telescoped over a rod which extends between the two links, so as to bias the links into switch-closed or switchopen positions. Both ends of the overcentering spring are thus moved as a result of which, the spring force for closing the contacts is high although the handle is easy to operate and swings through only a small arc. In other words, the spring is wound-up from both ends using two overcentering plates driven from the same handle, so that the handle does not have to move through as large an arc.
' Other features of the invention will be in part apparent from and in part pointed out in the following detail description taken in connection with the accompanying drawings, in which:
Fig. 1 is a side view illustrating a switching assembly embodying features of this invention;
Fig. 2 is a perspective view of the enclosure for the switching assembly, a door being removed;
Fig. 3 is a longitudinal section illustrating details of the enclosure for the switches;
Fig. 4 is a back plan .view of the door panels illustrating the interlock in various positions;
Fig. 5 is a view similar to that of Fig. 4 but showing the interlock mechanism in a trick position wherein the door may be opened without opening the switch;
Fig. 6 is a section taken on the line 6-6 of Fig. 4;
Fig. 7 is a section similar to Fig. 6, but showing details of the switch and its overcentering mechanism;
Fig. 8 is a back plan view of the overcenteringmechanism, illustrating partsin a switch-open position;
Fig. 9 is a view similar to that of Fig. 8 showing the parts moved to their switch-closed position;
Fig. 10 is a sectional view showing details of the movable contact element;
Fig. 11 is a view similar to Fig. 5, but showing an alternative embodiment of the door interlock; and
Fig 12 is a section taken on the line 12-12 of Fig. 11.
Referring now to the drawings, Fig. 1 illustrates a switch-assembly ll secured on mounting supports 3. Connection is made to bus'bars by plug-on devices 7, which project at the back of the switch assembly, whereas branch circuit connections are made at the ends of the switch assembly over the mounting supports 3.
In the illustrated embodiment, the switch assembly comprises a pair of three-pole fusible switches within a common enclosure. It is contemplated that the switching assemblies of different shape and size will be made up as prefabricated units for assembly on a switchboard. In general, the size and shape of an assembly will depend upon the capacity of the switch. Indeed, the size limitation may require that only one switch be contained in an enclosure where high capacity is required, but a primary object herein is to reduce the size of switch assemblies. For example, a twin three-pole fusible switch A assembly (each switch having a capacity up to sixty amperes at two hundred fifty volts) might be twelve inches long, five inches deep, and four and one-half inches wide.
The assembly comprises a channel-like enclosure having a back wall 9, side walls 11 and open ends 13. The side walls are joined at their ends near the front opening of the channel by angle members 15. A door 17 is hinged at each end of the enclosure to cover the front opening, and a bar 19 is fixed to extend across the front of the enclosure in the center where the doors meet. The
doors may have side flanges 21 overlapping the sides of the enclosure and detents 23 for releasably holding the doors closed.
Each door is conveniently hinged by means of a gutter cover panel 25, which is secured at 27 to the angle eleent at each end of the enclosure. The inner portion of the panel is formed with loops 29 shaped to extend through slots 31 in the door panel and also through similar slots 32 in the angle member 15.
' interiorly, the door carries switch-operating and doorinterlock mechanism. The latter has the function of normally preventing opening of the door when the switch is closed, while permitting the door to be swung open when the switch is open, as when it is necessary to replace fuses. In addition, this mechanism is adapted to permit opening of the door with the switch in its closed condition by a trick procedure not obvious to the layman. Such a feature is desirable in order to permit a skilled electrician or maintenance man to inspect the switch without interrupting an important circuit.
The switch unit itself is relatively compact and is operated by an arm 33 projecting forwardly. When the door is closed, the arm is engaged by the switch-operating mechanism on the inner face of the door, but the mechanism disengages from the door as the door is swung open. The door itself is held in a closed position by a 75 spring bolt 35 contained within the center bar 19 of the enclosure. The bolt, in turn, cooperates with a rotary keeper 37, which is operated by an exterior handle 39. The switch-operating arm 33 is rotatable between switchclosed and switch-open positions, and may be also rotated beyond the switch-open position against a slight spring bias to a door-opening position, as illustrated by dotted lines at the right side of Fig. 4. This slight bias normally maintains the keeper in a position which prevents inadvertent opening of the door with the switch off.
More particularly, the handle 39 is secured over a collar 41 having a flanged periphery in sliding engagement with the outer face of the door. The keeper 37 has an inner circular flange 43 received within a hole 45 in the door to form an axis of rotation, and arcuate slots 4-7 are out about this axis. The slots accommodate screws 51, which secure the keeper 37 to the flanged periphery of the collar. Accordingly, the handle is firmly supported for rotation, the slots 47 limiting the degree of rotary movement.
In the illustrated embodiment, the keeper plate 37 is formed with an inwardly displaced, notched periphery 49, which is movable beneath the spring bolt 35 of the door lock. The two bolts for a twin unit are contained in a small box 36 for movement toward and away from one another, a spring 38 providing the bias. It will be understood that the handle may be moved to certain positions wherein the keeper 37 is clear of the bolt in order to permit opening of the door, while movement of the handle to other positions results in the periphery 49 of the keeper being in locking engagement with respect to the bolt. The bolts are beveled in order to permit closure of the door when the keeper is in a door-locking position, a feature which is desirable because the door may have to be closed with the handle in its switch-closed doorlocked position. Although a spring bolt is shown, the keeper might cooperate with a fixed portion of the enclosure, such as a lug struck from the side wall of the enclosure. Other variations will suggest themselves to those skilled in the art.
The handle also operates a socket rotatably mounted on the back of the door. The end portion of the switch arm 33 is turned over at 57 (Fig. 7) so as to lie parallel with the door (when the door is closed) and seat within the socket 55. Also, a stud 59 projects within the socket on its axis of rotation, and when the door is closed, this stud engages within a hole 61 in the switch arm. As such, the stud 59 provides support for the forward end of the arm on its axis of rotation. Both the socket and stud may be beveled to facilitate proper alignment with the switch arm, as the door is closed. The socket is connected to the handle for actuation thereby, as by a link 63 pivoted to both the socket and the keeper 37.
The switch itself comprises a movable contact element 65 cooperating with fixed contacts 67 and 69, all contained within a base 71 of insulating material. The switch arm 33 extends rearwardly through this base between the fuses and contacts to operating mechanism at the back. The mechanism is contained in a shallow box 73, the front of which serves as a supporting panel for the movable contact element.
More particularly, the base is formed with a front wall 75 and end walls 77, which define a passage for movement of the movable contact element 65. Fused clips 79 may be mounted on the front wall for convenient access through the door opening. One of the fuse clips is connected to a branch circuit terminal 81 at the outer end, whereas the other fuse clip is connected at 83 to one of the fixed contacts 67. The other fixed contact 69 extends to a terminal at the inner end of the housing for connection with a bus-connecting strap 85. The plug-on bus connectors 7 extend from these straps for connection with the bus bars through an opening 87 of the back of the enclosure (Fig. 1).
The fixed contacts 67 and 69 project inwardly within the passage of the housing as resilient prongs in spaced parallel relationship to one another and to the base panel. The movable contact element 65 has an insulated body containing movable contact 66 adapted to be moved into and out of bridging engagement with the fixed contacts upon reciprocation of the contact element within its passage.
The quick-make and break operating mechanism is of a type adapted to prevent a dead-center condition wherein the movable contact is in partial engagement with the fixed contacts. In other words, the movable contact does not shift into or out of engagement with respect to the fixed contacts until the linkage overcenters.
The linkage has a crank operating a pair of pivoted links with a spring compressed therebetween. The switch arm 33 extends through an arcuate slot 89 in the back panel 91 and is folded over at 93, so as to lie flat against the panel. This folded over end portion 93 of the switch arm acts as the crank and is pivoted on a pin 95 fixed on the panel. The first overcentering link is a plate 97 secured upon this pin in overlying relationship with the crank. The other link is a plate 99 pivoted adjacent pin 95 on a second pin 101 also fixed on the back panel. The inner end of plate 99 is formed with a notch 105 adapted to be engaged by an car 107 formed on the crank. The crank additionally includes an upturned lug 109, which is received within a somewhat larger slot 111 in the plate 97. A connecting rod 113 is then mounted at a shifting pivot 115 upon plate 97. Spring 117 is telescoped over the rod, and the rod extends through an opening in the far end 119 of the other plate 99, where the spring is held in compression at 119.
The movable contact elements 65 (there being three in three-pole switches) are mounted upon a sliding plate 120 having a stud 121 projecting rearwardly through a slot 123 in the back panel. This stud also passes through a somewhat larger opening 125 formed in the pivoted plate 97. The larger opening 125 provides for a lost motion connection tending to prevent engagement or disengagement of the movable contact until the device overcenters, and also applies greater leverage to the stud as the contacts are closed.
With the switch open, the plate 97 is driven clockwise against a stop 127 and the other plate 99 is forced counterclockwise by the spring 117 against a stop 129. As the crank 93 and arm 33 are rotated, plate 97 is moved by lug 109 counterclockwise (Figs. 8 and 9) and plate 99 in a clockwise direction, the overcentering spring being compressed. The pivotal connection 115 of rod 113 is thus moved toward its overcentering position, defined generally by a line between the axis 95 of plate 97 and the point 119 at the opposite end of the spring 117. Similarly, plate 99 is moved clockwise by ear 107, so as to apply additional compression to the spring. As plate 97 is rotated, the end 119 approaches its overcentering position, as defined by a line through the axis 101 and the other end 115 of the rod.
It will also be noted that the pivot pin 115 for rod 113 is received within a convoluted slot, so that it may shift relative to the plate or link 97. The slot is shaped to provide end positions 131 and center position 133, which is somewhat closer to the axis 95. Normally, the pivot pin 115 is forced by spring 117 into one of the end pos tions 131, but when the links 97 and 99 are moved from their stops, the pivot point 115 may shift into its center position 133. The arrangement of parts is such that this shift occurs slightly before the links reach points at which overcentering would otherwise occur, and the shift of the pin 115 is then sufficient to overcenter both links. Accordingly, there is no dead-center position wherein the links might rest with the spring 117 under full compression. Up to the instant at which the pivot 115 shifts, the bias of spring 117 tends to return the links to their original positions.
Another feature to be noted is that the'movable contact elements 65 are moved very little except after the linkage overcenters. A little movement is desirable to overcome the static friction of the contacts, but the circuit is not broken until overcentering occurs. This action is in part attributed to the lost motion between the stud 121 and its associated receptacle 125. A lost motion effect is also afforded by the shift of the pivot pin 115. That is, the lateral shift of this pin causes the linkage to overcenter at a position somewhat prior to what would otherwise be the overcentering point. As will be apparent from the showing of the linkage in switch-closed and switch-open positions, the lever arm between axis and stud 121 is reduced and the force more nearly tangential in the closed position. Also, the thrust of the spring is nearly tangential in both positions, because of the move ment at 119. A powerful linkage is desirable in order to permit operation with high contact pressures. The linkage shown develops its maximum leverage when the contacts are closed, the force decreasing and rate of movement increasing when the contacts are open.
An additional feature of note is the action of the two overcentering links. The second link has the effect of relieving some of the compression in the spring, as compared with a system'having a single link and a spring otherwise fixed at one end. Conversely, the two driven links permit a greater and faster wind-up of the spring as compared with a single link and fixed point at 119. For this reason, the handle is easy to manipulate at its extremes of movement and swings through a small arc, although the compression at the overcentering point is high. The operator can more readily move the handle from either the switch-on or switch-off position, so as to gain momentum as the spring force increases rapidly toward the overcentering point. Immediately after overcentering, the spring force is high, and the momentum of the parts is sufficient to carry them to their opposite positions, although the spring force itself falls off rapidly.
It should be understood that one of the problems with contact switches is that of reducing the movement of the parts without making the switch more difficult to manipulate. In other words, when the spring force is high, the usual procedure has been to increase the mechanical advantage so that the handle moves a greater distance. The linkage disclosed operates in a different way.
Referring now to Fig. 11, there is shown a variation of the door interlock. In this instance, the spring bolt 235 is mounted in a housing 236 on the door 17 and cooperates with a slot in the cross bar 36. Although, the bolt is spring biased into the slot to lock the door, it can be retracted by means of a knob 237, which projects through a slot 238 from the front of the door. This knob is rearwardly connected to a latch arm 239 which is pivoted at 240. The latch arm then has an car 241 engageable with the periphery 49 of a keeper, the parts otherwise being similar to those described previously. When the keep is in its normal switch-closed position, the ear 241 prevents retraction of the latch arm, and the door cannot be opened. The bolt can be retracted to release the door by rotating the keeper to the trick position (Fig. 11) or to the switch-open position, in either of which events, the car 241 is free of the keeper so that the latch bar can be moved by its knob to retract the bolt.
From the foregoing description, it is apparent that those skilled in the art will understand the structure, function and mode of operation of the invention herein disclosed, and appreciate the advantages thereof. Although one embodiment has been disclosed in detail, it is to be understood that the invention is not limited thereto, but the drawings and description thereof are to be understood as being merely illustrative. For example, there may be several bases 77, each corresponding to a separate pole, or the base may be split in the other direction so that there is no portion thereof extending over the movable contact or contacts. It is realized that many modifications and variations will present themselves to those skilled in the art without departing from the spirit of this invention or the scope thereof as set forth in the appended claims.
Having thus described the invention, 'what is claimed and desired to be secured by Letters Patent is:
1. In a switch of the character set forth having a base panel and a movable contact mounted for movement across the panel; the improvement comprising the operating plate pivoted on said panel for swinging movement,
a contact-actuating element mounted for movement along a substantially rectilinear path between switch-open and switch-closed positions, said element being driven by said pivoted operating plate over said rectilinear path between switch-open and switch-closed positions, said operating plate being disposed With its rotational axis on one side of said rectilinear path opposite the switch-closed end thereof, whereby the plate develops increasing leverage with respect to the element adjacent the switch closed position decreasing leverage adjacent the switchopen position.
2. In a switch of the character set forth having a base panel and a movable contact mounted for movement thereon; the improvement comprising first and second 3 operating plates pivoted on separate axes offset from one another on said panel for movement between switch-on and switch-off positions, an operating arm rotatably engageable with both of said pivoted plates, a spring mounted with its ends engaged in the respective plates so as to be compressed thereby upon pivotal movement of either plate, and means on said operating arm in driving engagement with each of the two plates during compression of the spring upon rotation of the operating arm in either direction so as to move the opposite ends of the spring simultaneously together as the operating arm is rotated in either direction, thereby permitting a relatively short swing of the operating arm to compress and overcenter the spring, and means connecting the movable contact to at least one of said plates.
References Cited in the file of this patent UNITED STATES PATENTS 2,361,535 Evans Oct. 31, 1944 2,479,266 Rowe Aug. 16, 1949 2,515,449 Hammerly July 18, 1950 2,645,688 De Smidt et al. July 14, 1953