CA1044292A - Disconnect switch with modular arc chutes - Google Patents

Abstract

Abstract of the Disclosure A three-pole disconnect switch includes a cross-bar which is rotatably mounted to a housing and pivots three movable contact blades between opened and closed positions. Each movable contact blade is removably mounted to the crossbar and makes slidable electric contact with a connector. When in its closed position, each movable contact blade makes electrical connection with a stationary line contact. Modular arc chutes are slidably received in mating cavities formed in the housing above each set of contacts and a pair of auxiliary contact cartridges are received in chambers formed in the housing between the main contacts. A
trip mechanism is mounted to the side of the housing and couples one end of the crossbar to a manually operated handle.

Description

This application is a divisional of Canadian patent application Serial No. 232, 970 filed August 6, 1975.
The field of the invention is disconnect switches, and more particularly, manually Gperated disconnect switches having a set of movable contact blades which are pivoted by rotating a crossbar between an opened and closed position.
As illustrated in U.S. Patent No. 1,918,248, the crossbar which carries the movable contact blades is rotatably mounted to an in-sulating block that is typi-call~ mounted inside a cabinet and the crossbar is coupled to a handle mounted on the exterior of the cabinet through a spring loaded trip mechanism. The handle and associated trip mechanism may be mounted to one side of the disconnect switch, or as shown in U.S. Patent No. 3,602,676, the handle may be mounted to the front of the cabinet and its trip mechanism coupled to a point intermediate the ends of the crossbar.
When in their closed position, the movable contact blades electrically connect with a set of stationary contacts to conduct electric current from a set of input terminals to a set of output terminals. As illus-trated in the above cited U.S. Patent No. 3,602,576, each movable contact blade is typically connected to an output terminal through a flexible conductive strap, or pigtail, that allows the movable contact blade to be freely pivoted between its opened and closed positions.
As illustrated in U.S. Patent No. 3,684,849, the current carrying capacity of disconnect switches is often ~s :
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--1-- ' enhanced by employing arc chutes. Such arc chutes are comprised of a series of metallic deionization plates which are mounted to the insulating block and positioned directly above each movable contact blade.
~rcs which may result when the disconnect switch is opened are cooled and eventually extinguished by the deionization plates in each arc chute.
Disconnect switches are often employed with other electrical components to form control circuits such as motor starters. In such control circuits the disconnect switch serves not only to control the main electrical power through the operation of its movable contact blades, but also, to control the operation of other elements in the control circuit through the operation of auxiliary contacts which are mounted to the insulating block. The number and nature of such auxiliary contacts vary with each particular application of the disconnect switch and, therefore, these are typically fastened to the insulating block at any point which allows them to be mechanically coupled to the rotatable crossbar.
Prior disconnect switches are difficult to maintain and service. For example, if a movable contact blade is to be replaced, the arc chute located directly above j it must be removed and the flexible strap which connects it with the output terminal must be unfastened before the blade can be detached from the crossbar. Although some prior art structures allow the arc chutes to be removed and replaced as an integral unit, the fastening devices which hold such arc chutes to insulating blocks are often accessible only by removing the insulating .,.,~ .
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bloc~ ~rom its enclosure. Also, although prior au~iliary contacts are typically enclosed in self-contained cartridges, these cartridges are mounted to the front or s.ide of the insulating block using S fastening means which may not be easily accessible when the disconnect switch is mounted within its enclosure.
The present invention relates to an improved disconnect switch which is particularly easy to service and maintain. More specifically, the discon-nect switch includes a base having a pair of integrally formed side walls which de~ine a housing and an integrally formed divider wall which defines a pair of compartments within the housing; a crossbar mounted to the base for rotation about a horizontal actuation axis, the crossbar extending horizontally through each of the compartments; a plurality of movable contact blades, one disposed in each of the compartments and each fastened to the crossbar for swinging motion about the actuation axis between an opened and a closed position; a plurality of stationary line contacts mounted to the base, each of the stationary line con-tacts being disposed in one of the compartments to make electrical contact with the movable contact blade therein .
when the movable contact blade is in its closed position;
and a plurality of modular arc chutes, each separately mounted to the base and disposed within one of the compartments, and each including a case which supports a plurality of deionization plates in vertical, spaced relation immediately above the movable contact blade within the compartment.

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The present invention will enable one to provide a disconnect switch in which assembly and maintenance of its elements is facilitated. The modular arc chutes are easily removed by pulling them from their mating cavities. The deionization plates are thus easy to inspect as well as the stationary line contacts which are located behind the modular arc chutes.
The present invention, in conjunction with that described in copending Canadian application Serial No.
232,970, filed August 6, 1975, will now be described with reference to the accompanying drawings, in which~
Fig. 1 is a perspective view of the disconnect switch with parts removed and parts cut away, Fig. 2 is a front view of the disconnect switch of Fig. 1, Fig. 3 is an exploded side view of the disconnect switch of Fig. 1, Fig. 4 i9 a side view with parts cut away of the disconnect switch of Fig. 1, Fig. 5 is a perspective view of the crossbar and associated movable contact blades which form a part of the disconnect switch of Fig. 1, Fig. 6 is a side view of the disconnect switch of Fig. 1, . ~ .
Fig. 7 is a perspective view of a modular arc chute which forms part of the disconnect switch of Fig. 1, Fig. 8 is a bottom view of the modular arc chute of Fig. 7, Fig. 9 is a bottom view of an auxiliary contact ~
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~Lo~æ~z cartridge which forms part of the disconnect switch of Fig. 1, Fig. 10 is a side view with parts cut away of the auxi]iary contact cartridge of Fig. 9, and Fig. 11 is a view in cross section of the auxiliary contact cartridge taken along the line 11-11 in Fig. 10.
Referring particularly to Figs. 1-3, a two-part housing 1 is formed by a base 2 and a back 3 which are fastened to a mounting plate (not shown in the drawings) by a set of screws 4O The base 2 and back 3 are each molded from an electrically insulating thermoset phenolic material such as that sold commercially under the trademarks "SI 45 DUREZ" and "Plenco 509." The housing 1 rotatably supports a crossbar 5 which is journaled to a pair of spaced side walls 6 and 7 and which runs transversely through the interior of the housing 1 along a horizontal actuator axis 8. The housing 1 is divided into three compartments 9, 10 and 11 by a pair of integrally molded vertical divider walls 12 and 13.
The houslng 1 encloses a three-pole, single throw disconnect switch and each of the compartments 9-11 encloses the elements of one pole. The three poles are identical, and as shown best in Figs. 1 and 4, each includes a movable contact blade 15 which is fastened to the crossbar 5 and pivoted about the actuator axis 8 between an opened and a closed position. The movable contact blade 15 is made of copper and includes an operating end which is received between the jaws of a stationary contact 16. The stationary contact 16 is made of copper and is mounted to a metal strap 19 in ` `;

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the plane of the movable contact blad~ 15. The metal strap 19 is fastened to a back wall 17 by a screw 18 that is reeeived in a threaded opening formed therein and it supports an input terminal 21 that is fastened to the strap 19 by a screw 22. When the crossbar 5 is rotated to its closed position, the movable contact .- :: -blades 15 are pivoted about the actuator axis 8 and the operating end 23 on each movable contact blade 15 ~.
is received by the jaws of its associated stationary ~ .
line contacts 16. Electrical connection is thus made .
between the three input terminal lugs 21 and the movable . ~ ~
contaet blades 15. -~ ; -Located within each of the compartments 9-11 is a ~ ::
stationary connector 25 which electrically connects each movable contact blade 15 with an output terminal :~
26. As shown best in Figs. 1, 2 and 4, the connectors 25 are identical in construction to the stationary contacts 16 and they are fastened to a metal strap 27 which is in turn fastened to the base 2 by a serew 29.
The output terminal lug 26 fastens to the lower end of the strap 27 by means of a screw 30 and the strap 27 loops upward and forward to provide an integral mounting plate 31 for a fuse assembly (not shown in the drawings) whieh may be mounted dlrectly beneath the disconnect switch~. Whereas the jaws of the stationary contacts 16 extend forward, the jaws of each connector 25 extend ~ :~
rearward and reeeive the lower end 32 of the movable eontaet blade 15. As the movable eontact blades 15 are pivoted between the opened and closed positions, the lower end 32 on each maintains continuous electrical .-: . , . - . , :.,". : . ~

-contact with the jaws of its associa~ed connector 25.
Therefore, when electrical connection is made between the movable contact blades 15 and stationary contacts 16, three conductive paths are completed between the input terminals 21 and output terminals 26 on the dis-connect switch.
To facilitate the removal of the movable contact blades 15 for inspection and, if necessary replacement, each blade 15 is removably fastened to the crossbar 5.
Referring specifically to Fig. 5, each movable contact blade 15 is inserted through a transverse opening 35 in the crossbar 5 which is substantially rectangular in shape and which contains a detent mechanism that holds the blade 15 in place. The transverse openings are positioned along the actuator axis 8 to align the movable contact blades 15 in the planes of their associ-ated stationary contacts 16. The detent mechanisms include a pair of opposing metal retaining springs 36 each of which has a convex face 37 that is bounded at its ends by outwardly extending ears 38. A semispherical protrusion 39 is formed in the center of each face 37 and is received in an opening 40 which is formed through the movable contact blade 15. The retaining springs 36 are positioned within each transverse opening 35 to face one another. The ears 38 wrap around and clamp against recessed surfaces 41 that are formed in the crossbar 5 alongside the transverse openings 35, and the protrusions 39 are sprung towards one another to pinch the movable contact blade therebetween. By grasping the movable contact blade 15 with a suitable instrument, : . .. ,, , . : ., . , ~

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i~ can be removed by pulling it from between the retaining springs 36. The movable contact blade 15 -' is replaced by sliding it into ~he transverse opening 35 until the protrusions 39 snap into place in the opening 40.
Positioned within each compartment 9-11 and located directly above each movable contact blade 15 is a modular arc chute 44 which serves to extinguish : . .
any electrical arc that may be generated when the movable contact blades 15 are pivoted from their closed position to their opened position. Referring particularly to Figs. 1, 7 and 8, each modular arc chute 44 includes a two-part case 45a and b which is molded from a suit-able thermoset polyester insulating material and which is held together by a pair of rivets 43. The case 45 includes an overhang portion 46 which extends rearward and provides an insulating barrier directly above its associated stationary contact 16. The case 45 also includes a pair of side walls 47 which extend downward to form an archway 48 through which the operating end 23 of the movable contact blade 15 swings when pivoting between its opened and closed positions. A set of six rectangular slots 49 are formed vertically through the case 45 and each slot 49 receives a metal deionization plate 50. The plates 50 are thus aligned one in back of the other in closely spaced vertical planes, and . .
each is retained in its associated slot 49 by a pair of outwardly extending ears 51 which rest in pockets (not shown in the drawings) formed in each slot 49. Each deionization plate 50 includes a pair of downward extending a2 legs 52 which form an arch through which the operating end 23 of the movable contact blade 15 passes. AS is well known in the art, the electrical arc which is generated when the movable contact blade 15 opens circuit is broken into a seri~s of short arcs by the successive deionization plates 50, and these are extinguished by the cooling effect which the deionization plates 50 provide. It can be appreciated by those skilled in the art that the number and spacing of the deionization plates can be varied to alter -the current interrupting capability of the switch.
Each modular arc chute 44 is slidably received in a mating cavity 53 which is integrally formed within each of the compartments 9-ll above the crossbar 5.
Referring particularly to Fig. l, each cavity 53 is a substantially rectangular cavity which is defined along one of its vertical boundaries by one of the upright walls 12, 13 or 7 and which is defined along its top by an overhang 54 that is integrally formed on each of the walls 12, 13 and 7. Step-shaped barrier walls 55 are integrally formed to the base 2 within each compartment 9, lO and ll, and these form both the lower boundary of each cavity 53 and its left side. The outer dimensions of each modular arc chute 44 are slightly tapered to provide a wedging effect when the arc chute 44 is inserted into its cavity 53 from the front. Each modular arc chute 44 may be removed separately by pulling it straight forward from its cavity 53.
As shown best in Figs. 1-3, a cover 58 is mounted to the front of the housing l to substantially enclose '~ ' '~ '` ' _g_ L,~Z3~
that portion of each compartment 9, 10 and 11 above the barrier wall 55. The cover 58 is rnolded from a thermoplastic, flame retardant, polypropylene material, and it is fastened -to the base 2 by two pairs of integrally molded prongs 59 and a pair of captive screws 60. As shown best in Fig. 1, the prongs 59 are received in openings 61 which are formed on the front edges of the divider walls 12 and 13 and the screws 60 are received in openings 62 which contain threaded inserts. Referring particularly to Fig. 2, a set of three windows 63 are formed in the cover 58 and each is aligned directly in front of the archway 48 of a modular arc chute 44. Thus, when in their opened position, the operating end 23 of each movable contact blade 15 is readily visible through one of the windows 63 and can be easily inspected for wear. As shown in Figs. 3 and 4, a set of three stops 64 are integrally molded on the back side of the cover 58 directly above the windows 63. When the screws 60 are tightened, the stops 64 bear against the forward ends of the modular arc chutes 44 to retain them tightly ~-in their cavities 53. When the arc chutes 44 are to be removed, the captive screws 60 are unfastened and the ;
cover 58 is folded downward about a hinge 65 to expose these cavities 53.
As indicated above, when the disconnect switch is used in control circuits it is often necessary to operate auxiliary contacts. In the preferred embodiment described herein, provisions are made to mount a pair of auxiliary contact cartridges to the housing 1 and couple their ~$J~
operating elements to the crossbar 5. Referrin~
particularly to Figs. 1, ~ and 4, a pair of auxiliary chambers 67 are formed in the housing 1 between the poles contained within the compartments 9, 10 and 11.
Each auxiliary chamber 67 is substantially rectangular in shape and extends rearward from the front of the base 2 to its back wall 17~ The top and one side boundary of each chamber 67 are de~ined by the stepped barrier walls 55 in the compartments 10 and 11, the other side boundary of each is defined by a portion of the divider walls 12 and 13, and the bottom boundary of each is defined by a ledge 68 which is formed in each of the divider walls 12 and 13. A pair of rectangular openings 63 are formed in the cover 58 directly in front of the auxiliary chambers 67 and an auxiliary cartridge 70 is inserted into either chamber 67 through one of the openings 63. As shown best in Fig. 3, a pair of locking mechanisms 71 are integrally formed on the -~
back side of the cover 5g, and each locking mechanism 71 extends rearwardly into one of the auxiliary chambers -~
67. The locking mechanism 71 engages and firmly retains the auxiliary cartridge 70 in place.
Referring particularly to Figs. 5 and 9-11, each auxiliary cartridge 70 includes a relatively long slender case 72 which is molded from a thermoplastic polyester insulating material. A cam member 73 is slidably mounted to the bottom wall of the cartridge 70 and it includes a rectangular coupling element 74 which extends downward therefrom to engage one of two actuator elements 75 on the crossbar 5. As shown best in ~ig. 5, each . ~

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actuator elemen~ 75 includes a pair oE closely spaced helical walls 76 which are integrally formed to the crossbar 5 and extend radially outward therefrom to define a channel therebetween for the coupling element 74. When the crossbar 5 is rotated about the actuator axis 8, the cam member 73 on each auxiliary cartridge 70 slides along an axis which is parallel to the ;
actuator axis and which is indicated in Fig. ll by the arrows 77.
The sliding motion of the cam member 73 operates a set of auxiliary contacts 78 and 79 which are mounted inside the case 72 of each auxiliary cartridge 70.
Reerring particularly to Figs. lO and ll~ one of the contacts 79 is stationary and is connected to a terminal lug 80 by a bus 81 and the other contact 78 is supported by a movable contact arm 82 which connects to a terminal lug 83 through a bus 84. A cam follower element 85 is pivotally mounted to the case 72 and located directly beneath the movable contact arm 82. As the cam member 73 slides along its axis 77 in response to the rotation of the crossbar 5, the cam follower 85 operates the movable contact 78 to open and close the auxiliary contacts.
It should be apparent to those skilled in the art that many variations can be made in the contact structure within the auxiliary cartridges 70 and for a more detailed description of the particular auxiliary cartridge 70 described herein, reference is made to copending Canadian patent application Serial No. 220,229 which was filed on February 17, 1975, and which is entitled "Auxiliary Switch ~or Electromagnetic Contactor." Referring particularly ~;

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to Figs. 1, 2, 5 and 6, a trip mecharlism 88 is mounted to the left side wall 6 of the housing 1 to couple the crossbar 5 of the disconnect switch with a manually operated handle (not shown in the drawings). The trip mechanism 88 includes a metal frame 89 which is mounted by a set of screws 91 to ears 90 that are integrally formed on the side wall 6. The frame 89 is symmetrical about a vertical plane and it may be mounted in a similar manner to the right side wall 7 of the disconnect switch.
10 A set of four integrally molded ears 90 are formed on the right side wall 7 to mount the trip mechanism 88.
The handle (not shown in the drawings) operates through a coupling arm 92 which fastens to the upper end of a pivot plate 93 that is rotatably attached to the frame 89. A trip spring guide 96 connects the bottom end of the pivot plate 93 to the frame 89 and when the handle is operated, the pivot plate 93 is rotated about the actuator axis 8 between an opened and closed position.
A trip spring 94 surrounds the guide 96 and provides a strong snap action in both directions. The pivot plate 93 is connected to the crossbar 5 by a pair of tabs 95 that engage arcuate coupling slots 97 which are integrally ~:
molded to the ends of the crossbar 5. The mounting ears 90 are symmetrical with respect to the actuator axis 8 to allow the trip mechanism 88 to be mounted to ei~her side of the disconnect switch and to couple with the ;~
exposed end of the crossbar 5.
A disconnect switch has been described which embodies the present invention. It should be apparent to those skilled in the art, however, that many variations can be ., .~1.~' -13- :

z made in this structure without departing from the spirit of the invention, and reference is therefore made to the following claims.
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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A disconnect switch, the combination comprising:
a base having a pair of integrally formed side walls which define a housing and an integrally formed divider wall which defines a pair of compartments within said housing;
a crossbar mounted to said base for rotation about a horizontal actuation axis, said crossbar extending horizontally through each of said compartments;
a plurality of movable contact blades, one disposed in each of said compartments and each fastened to said crossbar for swinging motion about said actuation axis between an opened and a closed position;
a plurality of stationary line contacts mounted to said base, each of said stationary line contacts being disposed in one of said compartments to make electrical contact with the movable contact blade therein when said movable contact blade is in its closed position; and a plurality of modular arc chutes, each separately mounted to said base and disposed within one of said compartments, and each including a case which supports a plurality of deionization plates in vertical, spaced relation immediately above the movable contact blade within said compartment.

2. The disconnect switch as recited in claim 1 in which a barrier wall is formed to said base within each compartment to define a cavity which slidably receives and retains one of said modular arc chutes.

3. The disconnect switch as recited in claim 2 in which said cavities open to the front of the base and a cover is fastened to the front of the base to retain the modular arc chutes in place.