US3350532A

US3350532A - Explosion-proof switch

Info

Publication number: US3350532A
Application number: US597008A
Authority: US
Inventors: Arthur I Appleton
Original assignee: Individual
Current assignee: Emerson Electric Co
Priority date: 1966-11-25
Filing date: 1966-11-25
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31

Description

A. l. APPLETON Oct. 31, 19a? EXPLOS ION-PROOF SWITCH 4 Sheets-Sheet 1 Filed Nov. '25, 1966 mm rm o N mm will s V. w W? i 0 V m% 3. a J, U H T a W YA i R L was 3 w I Oct. 31, 1967 3 I A. I. APPLETON EXPLOSION-PROOF SWITCH 4 Sheets-Sheet 2 Filed Nov. 25, 1966 INvEN'rcR An'ruua L APPLsTcw 1 h/adlgb 1%, 1/033 (9M A-r-rvs.

.Oct. 31, 1967 A. I. APPLETON 5 EXPLOSION-PROOF SWITCH I Filed Nov. 25, 1966 4 Sheets-Sheet 3 82 INVENTOR 94 I ARTHUR I. APPLEToN i y: W9%L74MM,VGJBI@4MAL v v ATTYS,

Oct. 31, 1967 A. l. APPLETON EXPLOSION-PROOF SWITCH 4 Sheets-Sheet 4 Filed Nov. 25, 1966 INVEN TOR ARTHUR LAPPLETaN Arrvs'.

United States Patent 3,350,532 EXPLOSION-PROOF SWITCH Arthur I. Appleton, Northbrook, Ill. (1701 Wellington Ave., Chicago, Ill. 60657) Filed Nov. 25, 1966, Ser. No. 597,008 9 Claims. (Cl. 200-168) The present invention relates generally to switches and more particularly, the invention relates to exposion-proof electrical switches which may be safely used in th presence of atmospheres containing flammable gases or vapors in quantities sufficient to product exposive or ignitable mixtures.

A primary object of the present invention is to provide an improved switch structure which is particularly suitable for use in the presence of highly explosive atmospheres.

Another object of the invention is to provide an explosion-proof switch wherein any are which may be formed between opening and closing contacts is self-contained well within the switch body and extinguished with assured isolation from the surrounding atmosphere.

Still another object of the invention is to provide an explosion-proof switch incorporating make and break contacts which provide a fast opening and closing of the circuit with the engagement and disengagement of the contact member taking place with a wiping action that not only insures an instantaneous completion or interruption of the circuit, but which provides for self-cleaning of the contact elements so that smooth dependable contacting surfaces are brought into engagement. It is a related object to provide. a switch of the foregoing character in which any hot gas and burnt metal fragments which may be formed between the contacting surfaces are also completely confined within the body of the switch with assured isolation from the surrounding atmosphere.

Yet a further object of the present invention is to provide an improved explosion-proof switch structure wherein a minimum of space is present wherein gases may be confined and explosive gases are effectively excluded from the switch contact area so that there is no chance of causinga chain-type explosive reaction even in highly explosive atmospheres.

Other objects and advantages of the present invention will become apparent as the following description proceeds, .taken in connection with the accompanying drawings wherein:

FIGURE 1 is an elevational view partly in section through a switch structure illustrative of the present invention;

FIG. 2 is a sectional view taken substantially in the plane of line 22 of FIG. 1;

FIG. 3 is a front elevational view of the switch of FIG. 1, with a portion of the operating handle housing broken away;

FIG. 4 is a sectional view taken substantially in the plane of line 44 of F IG, 1;

FIG. 5 is a sectional view taken substantially in the plane of line 5-5 of FIG. 1;

FIG. 6 is an end elevational view of a switch actuating mechanism;

FIG. 7 is a rear end elevational view of a switch illustrative of the present invention;

FIG. 8 is a side elevational view of a snap disc, with a portion broken away illustrating the snap disc contacts;

FIG. 9 is a rear elevational view of the contact disc in FIG. 8 with a portion of the insulator block broken away;

FIG. 10 is a fragmentary side elevational view, partially in section, showing a slightly modified form of snap disc contacts that may also be used in the switch shown in FIG. 1;

FIG. 11 is a front elevational view of the contact carryin disc of FIG. 10, with a portion of the insulating disc broken away;

FIG. 12 is a sectional view taken substantially in the plane of line 12--12 of FIG. 11; and

FIGS. 13, 14, 15, and 16 are illustrative diagrams in perspective showing the positioning stages of the switch contacts.

While a certain illustrative embodiment of the present invention has been shown in the drawings, it will be described below in considerable detail, and it should be understood that there is no intention to limit the invention to the specific form disclosed. On the contrary, the intention is to cover all modifications, alternative constructions, equivalents and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Referring to the drawings, more particularly FIGS. 1 and 3, there is shown an explosion-proof switch embodying the features of the present invention and comprising a casing, generally indicated at 20, having a sleeve-like extension 21 at one end and a generally square shaped flange portion 22 at its opposite end. The flange portion 22 is provided with suitable apertures for receiving bolts 23 to mount the casing on a conduit box housing 24 or the like. A suitable opening in the conduit box housing 24 receives a cable 26 having a plurality of conductors 27.

A generally cup-shaped switch operator housing 28 telescopes over the sleeve-like projection 21 of casing 20 and includes an outwardly projecting handle 30 for rotating the switch operator housing.

Referring to FIG. 3, the inner surface of the switch operator housing 28 is provided with radially inwardly extending pins 32 which cooperate with slots 34 on the outer peripheral surface of casing sleeve 21 so that the peripheral extent of the slot 34 defines the degree of rotation that may be effected between the switch operator 28 and the switch casing 21. v

For the purpose of indicating on and off positions of the switch operator 28, a pointer arm 36 extending radially outward from the outer peripheral edge of the switch operator housing points to suitable on-olf indications stamped or otherwise formed in the flange 22 at the rotational limit positions of the switch operator 28 as defined by the pins 32 and slots 34.

In order to prevent unauthorized tampering with the switch, suitable locking means 40, as viewed in FIG. 3, may be provided to receive a seal or lock thereby preventing the switch operator from being rotated. In the present instance, the locking means 40 includes an arm 41 projecting outwardly from the switch operator housing 28 and having an aperture adjacent its outer end. A second projecting arm 42 secured to the flange 22 includes an aperture that becomes aligned with the aperture in the arm 41 when, for example, the operator 28 is moved to the on position as shown in FIG. 3. A locking device (not shown) may be inserted through the apertures of

arms

41, 42 to maintain the switch in the on position. In accordance with one aspect of the present invention, a plurality of jumper or bridging members 46 are carried in an insulator block 47 which is bolted to the switch operator housing 28 by a plurality of bolts 48. The insulator block 47 telescopes within the sleeve 21 of the casing 20 with a sufficiently close fit so as to insure there is no open space for gas to accumulate, yet permitting the switch operator to be easily rotated by hand.

Referring to FIGS. 1, 2, and 3, conjointly, the bridging members 46 include a plurality of generally kidneyshaped contacts 50 disposed proportionately about the center axis of block 47 with the contacts 50 lying in recesses formed in the end face of the block 47 so that the contacts 50 present contact surfaces lying substantially in the plane of the block end face 51. Hollow sleeve members 52 are seated in axially extending bores formed in insulator blocks 47 leading to the inner sides of the contacts 50 and jumper strips 53 interconnect respective pairs of contacts 50 with the entire assembly 46 being held in place by bolts 54 passing through the jumper strips, sleeves 52 and threadably engaging threaded apertures formed in the inner faces of the contacts 50.

Disposed within a central opening in the block 47 is a cylindrical insert 58 having a hexagon-shaped socket 59 formed therein, the purpose of which will be discussed more fully below.

In carrying out one of the important aspects of the present invention, input circuit contacts are provided well within the switch casing to insure that opening and closing of the switch circuit takes place in complete isolation from the outside atmosphere. Thus, referring to FIG. 1, there is provided an insulator block 60 having a flange portion 61 which is bolted to the rear of the switch casing flange 22 by bolts 63. In order to insure that an effective seal is maintained between the block 60 and the mounting flange 22 and, also, in order to insure the retention of aligned positioning between the casing flange and block, the engaging surfaces of the block 60 and the mounting flange 22 are preferably roughened such as by the provision of suitable corrugations or threads 64. Seated in openings in block 60 are a plurality of conductor bars 66 which correspond in number to contacts 50.

For the purpose of connecting the conductor bars 66 to the conductors of cable 26 (FIGS. 1 and 7'), a plurality of terminal connectors 70 are provided, each of which includes a lug 72 bolted to the rods 66 by a suitable threaded fastener 73. Terminal clamps 74 secured to the lugs 72 by means of screws 76 or the like are provided to secure the conductors 27 to the conductor bars 66.

With the conductor wires 27 connected to the terminals 74 in the illustrative switch embodiment a pair of conductor bars 66 comprise input circuit contacts. The remaining airs of terminals 74 and conductor bars 66 will comprise output circuit contacts with respective pairs of the input and output contacts being electrically interconnected by means which can be rotated into and out of the circuit between conductor bars 66 and contacts 50.

In carrying out the present invention, a pair of interfitting

insulating discs

80, 82 are disposed between block 60 and block 47 with the discs carrying a plurality of contact assemblies 86 extending through openings 88 in the discs to present cooperating contact surfaces with the conductor bars 66 and contacts 50. Each of the contact assemblies 86 comprises a pair of contacts 92, 94 (FIG. 8) which are spring biased through a substantially U-shaped interconnecting conductor member 96. The

discs

80, 82 have aligned

central openings

97, 97a respectively, which are generally hexagonal shaped for receiving a sleeve-like shaft 100 having a portion 101 which, also being hexagonal shaped, receives the

discs

80, 82. The remaining portions of the shaft 100 are cylindrical including reduced diameter portions along the shaft permitting independent rotation of the shaft and

discs

80, 82 in a manner to be described below. Disposed within the central opening 102 of shaft 100 is a tubular shaft 104 having an enlarged hexagonal shaped end portion 106 which is received by the hexagon shaped socket 59 formed in insulator block 47.

In carrying out yet another aspect of the invention, means are provided for assuring substanially instantaneous completion or interruption of the circuit between the rotatable disc-carried contact assemblies 86 and the conductor bars 66, the respective contacting surfaces being engaged and disengaged with a wiping action that minimizes any. possibility of arcing and also provides for selfcleaning of the contact elements. For this purpose, a

detent mechanism, generally indicated at 110 (FIGS 1 and 6) interconnects the

shafts

100, 104 so that rotation of the shaft 104 exerts a torque upon shaft 100, the latter being restrained from roating during a portion of the rotation movement of shaft 104. After there is a sufficient build up of torque upon shaft 100 the restraining means for this shaft is triggered permitting shaft 100, carrying

discs

80, 82 and contact assemblies 86 to snap into engagement with or disengagement from conductor rods 66, depending upon the direction in which the shaft 104 is rotated. Thus, referring to FIGS. 1 and 6, an actuator member 112 having a suitable slot formed therein adapted to receive the flattened end portion 113 of shaft 104 has connected thereto by a threaded fastener 114 engageable with a suitable threaded opening provided in the end of the shaft 104. Actuator 112 is formed with generally triangular shaped bent-over lugs 116118 at its vertices. A torsion spring 120 with its coils disposed about shaft 104 and the

ends

122, 124 of the spring 120 crossed over one another bear against the lug 118 of actuator 112.

Secured to shaft 100 by a suitable slot and shoulder arrangement, is a disc actuator 126 which also is of generally triangular shape and including depending bentover lug portions 128-130 at its vertices. Bent-over portion 130 of the disc actuator 126 extends adjacent the lug 118 of actuator 112.

A pair of

trigger members

132, 134 are pivotally mounted on a pin 136 secured to the insulator block 60 by a suitable bolt 137. The

trigger members

132, 134 are oppositely oriented and biased towards one another by a torque spring 140 mounted on pin 136. Each of the trigger members is provided with a

slot

142, 144 respectively, adapted to receive

lugs

128, 129, respectively, on the disc actuator member 126. Shoulders 146, 148 on the outer ends of the

trigger members

132, 134, respectively, are disposed in the paths of

lugs

116, 117, respectively, of actuator 112 when it is rotated.

In order to more fully understand the mode of operation of the detent mechanism 110, reference is made to FIG. 6 wherein the lug 128 of disc actuator member 126 is seated in the slot 142. of trigger member 132 which for the present purposes is considered to be the position where the contact assemblies 86 are in alignment with the conductor bars 66 and will be referred to herein as the on position.

It should be understood as the ensuing discussion proceeds that while two input circuits and two output circuits on the switch are provided, there is no such limitation in actual practice, and the number of input and output contacts is determined, as desired, by the number of conductors to be employed andv the number of circuits to be completed. With the number of contacts selected as two pairs in the description of the illustrative form of the present invention, the contacts are proportionately distributed with a center to center arcuate distance of approximately 45. Thus, the actuator member 112 is dimensioned such that rotation of shaft 104 in turn rotates the actuator bringing lug 116 into engagement with shoulder 146 of the trigger 132 in approximately 22 /2 of rotation. At this point, the lug 116 pushes against the shoulder 146 and during subsequent rotational movement of actuator 112 through another 22 /z, the lug 128 is released from slot 142 in the trigger.

Since there is a build up of torque applied to the disc actuator 126 during the first 22 /2 of rotation of actuator 112 when the lug 128 is released, the disc actuator 126 W111 snap in the same direction as actuator 112 is rotated and lug 129 will seat into the slot 144.

The snap action of disc actuator 126, as previously described, rotates the shaft 100 so that contact assemblies 86 via their carrying

discs

80, 82 are moved out of engagement with conductor bar 66, this position being called off position. Rotation of the actuator 112 in the opposite direction brings lug 117 into engagement with the shoulder 148 of trigger member 134 releasing the lug 129 of disc actuator 126 and causing the disc actuator to snap mthe other direction until lug 128 stops in slot 142 of trigger 132.

In accordance with another aspect of the present in- I vention, provision is made for accommodating any hot gas and burnt metal fragments which may be formed between contacts -86 and conductor bars 66 and which also serve to extinguish any are that may be formed. Thus, referring to FIG. 5, generally tear-shaped recesses 150 are provided adjacent each of the openings in insulator block 60. The recesses 150* are disposed in the path which contact assemblies 86 rotate into and out of engagement with conductor bars 66 and since engagement and dis-v engagement occurs-through sliding contact, the recesses 150 will receive burnt metal fragments and the like dislodged or scraped from the contacting surfaces thus producing a self-cleaning action.

Referring to FIGS. and 11, there is shown an alternative form ofsnap disc contact assembly, indicated generally as 86a. In the present instance contact assemblies 86a each comprise a contact element 920 which will slidably engage with a corresponding kidney-shaped contact 50 (FIG. 2) and a substantially U-shaped conductor member 96a which by spring action urges contact 92a against the associated contact 50. The opposite end of the conductor member 96a is provided with an opening 152 adapted to receive rounded ends 154 formed on conductor bars 660. The peripheral edge of the openings 152 disposed the path which conductor bars 66 rotate into and out of engagementwith the opening 152 are provided with inwardly sloped surfaces or ramps 156 to assure positive seating and unseating of the rounded ends 154 in their respective contact openings 152.

In order to more fully explain the mode of operation of the illustrative switch, reference is now made to FIGS. 13, 14, 15, and 16 inclusive, where illustrative diagrams showing the positioning stages of the switch contact membets are shown.

Turning first to FIG. 13, the switch is shown in the 01f position such as when a switch operator housing is in its extreme counterclockwise rotatable position, as viewed in FIG. 3. The contacts 92 of contactassemblies 86, together with the

discs

80, 82 are approximately 45 out of alignment from the conductor bars 66. The generally kidney-shaped contacts 50 engage the contacts 92 when the switch is in the off position, however, the circuit between associated pairs of conductor bars and pairs of bridging members 46 still remains open. When the switch operator housing 28 is rotated a first 22% as herein shown in FIG. 14, the contacts 50 move with respect to the disc contacts 92 and conductor bars 66, the latter two still remaining out of alignment. Continued rotation of the switch and operator housing 28 through a subsequent 22 /2 triggers the

discs

80, 82 carrying the contact assemblies 86 as previously described, whereby contacts 92 slide along the surfaces of contacts 50 and contacts 94 slide into engagement with the conductor bars 66 completing associated pairs of circuits at the end of 45 of travel of the switch operator housing 28, as shown in FIG. 15. Since contacts 94 slide into engagement with the conductor bar 66 and, also, contacts 92 slide along the surface of contacts 50 there is little likelihood of arcing occurring between the contacts, and they are substantially self-cleaning for smooth dependable operation.

When turning the switch operator housing to the off position, by rotation thereof as herein shown in FIG. 16, during the first 22 /2", the contacts 50 slide along contacts 92, yet the circuit remains closed. During the second 22 /2 of rotation of the switch operator housing, the disc carried contact assemblies 86 are triggered and return again to the position shown in FIG. 13.

The kidney-shaped contacts 50 insure that the bridging members 46 are always in engagement with the disc carried contacts 92 as the switch operator housing is rotated to the off position. Thus, the circuit is broken only when the disc carried contacts 94 snap out of engagement with the conductor bars 66 and any are which might occur will be contained well within the sealed switch casing.

It is one of the features of the present switch that a minimum of space is present wherein gases may be confined and explosive gases are efiectively excluded from the switch contact area so there is no chance of causing a chain type explosive reaction even when operating in highly explosive atmospheres. Thus, insulating

blocks

47, 60 and

snap discs

80, 82 together with their respective contact assemblies substantially fill all available space within the switch casing leaving little or no voids where flammable gases or vapors can accumulate in quantities sufficient to produce any hazardous situations. The circuit is made and broken between conductor bars 66 and snap disc contacts 94 whereby any possibility of arcing remains confined well within the sealed casing.

I claim as my inventioni 1. An explosion-proof switch including a casing adapted to be secured to a conduit box housing or the like, comprising, in combination, a sleeve-like extension at one end of said casing, a generally cup-shaped switch operator housing telescoped over said sleeve-like extension and adapted to be rotated relative to said extension, a first insulator block mounted in said sleeve-like extension and secured to said operator housing for rotation therewith, said first insulator block having first and second contacts presenting contacting surfaces, bridging means for interconnecting said first and second contacts, a second insulator block spaced from said first block and mounted within said casing, said second block having first and second conductor bars adapted to be connected to an electrical circuit, disc means rotatably mounted between said first and second blocks, said disc means carrying first and second spaced contacts having contacting surfaces, said disc-carried contacting surfaces being slidably engageable with respective ones of said first block contacts and said conductor bars, actuating means connected to said disc for rotationally snapping said disccarried contacts into sliding engagement with said conductor bars, and means cooperable between said first insulator block and said actuating means for operating the latter upon rotation of the switch operator housing.

2. An explosion-proof switch as claimed in claim 1 wherein said first insulator block contacts are generally kidney-shaped so that engagement between said disc contacts is maintained until after the circuit between said disc contacts and conductor bars is broken whereby any possibility of arcing is confined well within the sealed switch casing.

3. An explosion-proof switch as claimed in claim 1 wherein said actuating means comprises a rotatably mounted, hollow, first shaft secured to said disc means, a second shaft disposed within the central opening in said first shaft, first and second actuator members secured to said first and second shafts, respectively, spring means interconnecting said first and second actuator members so that a first portion of rotation of said second shaft winds said spring to exert a rotational torque on said first shaft, a trigger member for restraining rotation of said first actuator member and means associated with said second actuator for releasing said trigger member during a second portion of rotation of said second shaft permitting said spring means to snap said disc-carried contacts into alignment with said conductor bars.

4. An explosion-proof switch as claimed in claim 1 wherein said second insulator block includes generally tear-shaped recesses formed therein adjacent said conductor bars and disposed in the path which said disc-carried contacting sufaces rotate into and out of engagement with said conductor bars.

5. An explosion-proof switch as claimed in claim 1 wherein said disc-carried contacts are spring biased into engagement with said first insulator block contacts and said conductor bars.

6. An explosion-proof switch as claimed in claim wherein said conductor bars include rounded end portions, said second disc-carried contact sufaces include openings adapted to receive said conductor bar rounded end portions, and the peripheral edges of said contact openings in the paths of said conductor bars including inwardly sloped ramps for assuring positive seating and unseating of said rounded ends in their respective contact openings.

7. An explosion-proof switch in accordance with claim 1 wherein said switch operator housing includes a radially inwardly extending pin, said casing sleeve-like extension includes a transverse slot on the outer peripheral surface thereof so that the peripheral extent of said slot defines the rotational limits of said switch operator housing with respect to said switch casing.

8. An explosion-proof switch including a casing adapted to be secured to a conduit box housing or the like, comprising, in combination, a sleeve-like extension at one end of said casing, a generally cup-shaped switch operator housing telescoped over said sleeve-like extension and adapted to be rotated relative to said extension, a first insulator block mounted in said sleeve-like extension and secured to said operator housing for rotation therewith, said first insulator block having a plurality of contacts presenting contacting sufaces, bridging means for interconnecting pairs of said contacts, a second insulator block spaced from said first block and mounted within said casing, said second block having a plurality of conductor bars adapted to be connected in electrical circuits, disc means rotatably mounted between saidfirst and second blocks, said disc means carrying a plurality spaced contacts having contacting surfaces, said disc-carried contacting surfaces being slidably engageable with respective ones of said first block contacts and said conductor bars for completing electrical circuits between pairs of conductorbars and first block contacts, actuating means connected to said disc for rotationally snapping said disccarried' contacts into sliding engagement with said conductor bars, and means cooperable between said first insulat-or block and said actuating means for operating the latter upon rotation of the switch operator housing.

9. An explosion-proof switch as claimed in claim 8 wherein said first insulator block contacts are generally kidney-shaped so that engagement between said disc contacts is maintained until after the circuit between said disc contacts and conduct-or bars is broken whereby any possibility of arcing is confined well within the sealedswitch casing.

References Cited UNITED STATES PATENTS 3,236,989 2/1966 Zavertnik 61 a1 200168 3,264,443 8/1966 Farina et al. 200-168 3,287,51-6 11/1966 Nielsen zoo-16s ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner.

Claims

1. AN EXPLOSION-PROOF SWITCH INCLUDING A CASING ADAPTED TO BE SECURED TO A CONDUIT BOX HOUSING OR THE LIKE, COMPRISING, IN COMBINATION, A SLEEVE-LIKE EXTENSION AT ONE END OF SAID CASING, A GENERALLY CUP-SHAPED SWITCH OPERATOR HOUSING TELESCOPED OVER SAID SLEEVE-LIKE EXTENSION AND ADAPTED TO BE ROTATED RELATIVE TO SAID EXTENSION, A FIRST INSULATOR BLOCK MOUNTED IN SAID SLEEVE-LIKE EXTENSION AND SECURED TO SAID OPERATOR HOUSING FOR ROTATION THEREWITH, SAID FIRST INSULATOR BLOCK HAVING FIRST AND SECOND CONTACTS PRESENTING CONTACTING SURFACES, BRIDGING MEANS FOR INTERCONNECTING SAID FIRST AND SECOND CONTACTS, A SECOND INSULATOR BLOCK SPACED FROM SAID FIRST BLOCK AND MOUNTED WITHIN SAID CASING, SAID SECOND BLOCK HAVING FIRST AND SECOND CONDUCTOR BARS ADAPTED TO BE CONNECTED TO AN ELECTRICAL CIRCUIT, DISC MEANS ROTATABLY MOUNTED BETWEEN SAID FIRST AND SECOND BLOCKS, SAID DISC MEANS CARRYING FIRST AND SECOND SPACED CONTACTS HAVING CONTACTING SURFACES, SAID DISC-CARRIED CONTACTING SURFACES BEING SLIDABLY ENGAGEABLE WITH RESPECTIVE ONES OF SAID FIRST BLOCK CONTACTS AND SAID CONDUCTOR BARS, ACTUATING MEANS CONNECTED TO SID DISC FOR ROTATIONALLY SNAPPING SAID DISCCARRIED CONTACTS INTO SLIDING ENGAGEMENT WITH SAID CONDUCTOR BARS, AND MEANS COOPERABLE BETWEEN SAID FIRST INSULATOR BLOCK AND SAID ACTUATING MEANS FOR OPERATING THE LATTER UPON ROTATION OF THE SWITCH OPERATOR HOUSING.