US 2368914 A
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MAKERS R BREAKERS, U u UNI DMW @Garon me:
K Feb- 6, 1945. l.. R. BOWEN 2,368,914
JACK SWITCH Filed March l5, 1943 2 Sheets-Sheet 1 ji :EIELL 2/ y 27 33 2P@ 43 47 j? 47 45 k2 INVENToR.
MAKERS L BREAKERS,
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JACKI SWLTCH Mnclh 15, 19433 if4 EISA:
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Patented Feb. 6, 1945 UNITED STATES PATENT OFFICE JACK SWITCH Lloyd R. Bowen, Oakland, Calif.
Application March 15, 1943, Serial No. 479.295
This invention relates to apparatus for permitting ready introduction of test instruments, or other temporarily used current-utilizing devices, into power lines.
It is an object of the invention to provide a line jack, for use in circuits carrying heavy current loads, with which a special plug member may be readily connected so as to observe current characteristics in lines feeding motors or other current-utilizing devices.
Another object of the invention is to provide, lrr a line jack, a pair of floating contact jaws which will insure proper engagement with a plug member inserted therebetween regardless of any slight variations in angular relationship between said contacts and the plug member.
A further object of' the invention is to providein a line jack, a pair of contact jaws arranged to separate in such a manner, upon insertion of a plug member therebetween, that arcing is conned to a limited marginal area thereof so as to preserve the main surfaces of the contacts against pitting and therebyv insure good subsequent elec trical engagement between the contacts and the plug member.
The invention possesses other objects and features of advantagel which, together with the foregoing, will be set forth in detail in the detailed description of the preferred form of the invention hereunto annexed. It is to be understood that the invention is not to be limited to the specic form thereof herein shown and described as various other modifications thereof may be employed which reside within the scope of the appended claims.
Referring to the drawings:
Figure 1 is a horizontal sectional view of the line jack of my invention. The plane in which the view is taken is indicated by the line l-I of Figure 2.
Figure 2 is a front elevational view of the line jack. A portion of the view is broken away so as to more clearly disclose the underlying structure.
Figure 3 is a cross-sectional View, to an enlarged scale,y of that portion of the apparatus lyingr in the plane indicated by the line 3--3 of Figure l.
Figure 4 isa View, similar to Figure l, showing the` position occupied by the contact jaws either' just prior to complete insertion of the plugl member therebetween or just prior to complete disengagement of the plug member from the contact jaws.
wire multiphase circuits.
Figure 5 is a front elevational view of the plus member.
Figure 6 is a vertical sectional View of the plug member taken in the plane indicated by the line 6 8 of Figure 5.
Figure 7 is a bottom plan view of the plug member.
In detail, the structure of my invention comprises a sheet metal cabinet 8, which may be secured to a building wall or other supporting structure, provided with a front panel 9, constructed of insulating material such as Bakelite. having therein a plurality of vertically alined and relatively spaced parts Il and secured to a marginal flange i2, formed in the cabinet 8, by means of screws i3 or by other suitable means. The panel 9 covers only a portion of the open front of the cabinet; sheet metal doors i4 being provided on one or both sides or' the panel 9 and movable, on hinges I5, to uncover the cabinet opening so that inspection of the apparatus within the cabinet, or the making of connections thereto, are facilitated. Spring latch fingers ll. secured to sides of the cabinet by anchor screws i8, have end lugs I9 overlying the outer surfaces of the doors I4 so as to releasably retain the latter in their closed position.
Mounted on spaced bolts 2|, which pass through the back of the cabinet and also through tubular ferrules 22 which space it from the cabinet walls, is a sub-panel 23 constructed of sheet Bakelite, slate or other such material from which switchboard panels are usually made, extending across the greater portion, vertically, of the cabinet chamber, and positioned directly in back of the front panel 9. The sub-panel 23 carries a plurality of sets of contacts by means of which temporary or extended connection may be made to power lines running into the cabinet and since each set of contacts is identical for each power line, it Will suice to describe only one set in detail.
In the drawings, the illustrated apparatus is intended for three phase circuits but, by providing two or more sets of contacts, the apparatus may be adapted to any set-up from the common two-wire A. C. and D. C. circuits to the plural In addition to being a duplicate of the adjacent ones, each set of contacts is made up of a pair of identical sections arranged symmetrically about the vertical medial axis of the sub-panel 23 and comprising a metal base plate 24 having, at one end, an upturned ange 213 from which projects a pair of guide pins 27. A spade lug 28 is secured to the other end of the base plate, by means of a. bolt 29 which passes through alined apertures provided in the lug, base plate and sub-panel, and is fitted with a sleeve 3| in which is secured, by means of a setscrew 32, the bared end of one of the current conductors 33 which enter the cabinet 8 through apertures 34 formed in each side thereof. A metal post 36 rises from the base plate 24, in spaced relationship to the flange 26 and is secured to the base plate by means of a screw 31 which passes through an aperture formed in a flange 38, formed on the post and engaging the base plate, and is engaged in alined threaded apertures formed in the base plate and in the sub-panel 23. I further provide an approximately U-shaped contactor having a jaw portion 39 and an arm portion 4I, the latter, at its end, being provided with a pair of spaced apertures 42, see Figure 3, in which the guide pins 21 are slidable and which are sumciently larger in diameter than the guide pins that the contacter is capable' of considerable pivotal movement relative to andin a direction paralleling the direction of slidable movement of the contacter along the guide pins. Coil springs 43, interposed between each arm portion 4| of the contactors and the adjacent posts 36, serve to urge the fiat surface of each jaw portion 36 of the contactors toward and against the corresponding confronting surface of the jaw portion of the other section of the contact set so as to thereby establish an electrical conductive path from one current conductor 33 through the baseplates 24 and the engaged contactors to the other oppositely alined current conductor 33. Screws 44 tapped into the posts 36 and the arm portions 4| of the contactors have their heads 46 entering the ends of the coil springs 43 so as to anchor the latter against displacement and a looped, flexible metallic ribbon 41 is engaged under the head of one screw vin each section of the contact set and also under a washer 48 and nut 49, carried by an extended one of the screws 44 on the post 36 so as to form a positive current bridge around the pivotal connection of the arm portion 4| of the contactor with the guide pins 21. It will be seen that, since the contactors are capable of floating and pivotal movement, the latter being possible about any point along the path of slidable movement of the contactors on the guide pins 21, any dierences in strength between the respective springs 43 will not adversely affect the quality of electrical engagement between the contact jaws 39 since irrespective of whether one contact jaw moves toward the other jaw at a faster rate or whether the said one contact comes to a position of rest angularly related to the surface of the sub-panel 23, the other contact jaw will be brought by its springs 43 into a complementary position so that the contact jaws will engage over their entire contacting surfaces.
Means is provided, for insertion into the cabinet C through the panel parts Il, for separating the engaged contact jaws 39, so as to break the flow' of current between opposite ones of each pair of conductors 33, and for electrically contacting the separated jaws so that branch circuits may be fed from the conductors. As is best shown in Figures to '7 inclusive, I provide a plug member composed preferably, of a unit piece of insulating material, suchas sheet Bakelite, having an upper handle portion 5| provided with a finger hole 52 and a channeled reinforcing grip 53 secured to the upper edge of the handle D01- tion 5I by means of non-metallic pins 54.
Tongues 56 formed integrally with the Bakelite sheet and equal in number and spacing to the number of parts provided in the panel 9, depend from the lower edge of the sheet. Overlying the sides of the tongues 56 are separate metal plug fingers 51 each provided at its lower end with a bevel 58, so as to provide a pointed end on each plug, and at its upper end being secured, by screws 58 to a terminal block 59 provided with an aperture 6| for the reception of the bared end of a branch conductor, not shown, the latter being secured in the terminal block 59 by means of a setscrew 62 tapped into the terminal block to intersect the aperture 6|. The metal plug fingers 51 are secured to the tongues 56 by bolts 63 and nuts 64, which pass throu-gh alined apertures formed in the tongues and fingers, and plates 86 and bushings 61, the latter surrounding the bolts 63 and the latter underlying the heads and nuts, respectively, of the bolts, serve to electrically insulate the bolts from the metal lingers 51. A protective hood composed of sheets 68 of insulating material, overlying the terminal blocks 59 and secured to the handle portion 5| by clips 69 and bolts 1|, and skirts 12 secured, by screws 13, to and depending from the outer edges of the sheets 68, serve to guard the operators hand, gripping the handle portion of the plug member, from coming in contact with any of the current-carrying parts. Apertures 14, provided in theskirts 12 and alined with the setscrews 62,- permit the introduction of a'suitable tool such as a screwdriver to loosen or tighten the setscrews. f
As shown in Figure 4, the plug member is inserted through the panel parts the beveled prongs then passing .between and separating the contact jaws 39. When fully inserted, as shown in Figure l, the contact jaws will be completely separated, thus disrupting the electrical connections between the conductors 33, and will be ene gaged only with the metal fingers 51 on either side of the plug prongs. Thus current may be drawn from the separate conductors to actuate meters, whose leads have previously lbeen attached to the terminal blocks 59, or to other current consuming devices. Referring to Figure 4, it will be-seen that a desirable action takes place when the plug prongs are passed into engagement with the contact jaws, this action being accentuated if the movement of the prongs between the con-l tact jaws is rapid. As shown in Figure-4, entry of the prongs between the contact jaws tilts the latter so that their rearward ends remain in contact while the springs 43 are being compressed due to the separation of the jaws. Further movement of the prongs between the contact jaws will bring the point where the bevelled surfacesv 58.
of the fingers 51 intersect the side surfaces thereof in line with the force line of the springs, whereupon the contact jaws will rock to completely separated parallel positions thus breaking the mutual contact of the jaws at `their rearward ends. This series of actions, of course, occurs so quickly when the plug member is suddenly' thrustinto the cabinet, that a de'nite snap action occurs, finally separating the contact jaws so that arcing between .the jaws is reduced to'a harmless minimum. In the event that arcing should'occur, it is confined to the rearward ends of the contact jaws where it is not liable to cause pitting or the building up of metallic deposits-on the confronting faces of the jaws suihciently .to produce poor electrical contact between the jaws. It will also be seen that, in withdrawing the. plug member from the cabinet, the contact jaws 39 come together at their rearward ends, thus reestablishing the circuit between the conductors 33, before the fingers 51 disengage the contact jaws. This eliminates any arcing between the ends of the plug prongs and the contact jaws.
In use, a number of the line jacks described above will be spaced at intervals along supply lines to motors or other electrical equipment so that a patrolling inspector equipped with a plug member attached to suitable meters may make periodic inspections of the lines to insure that correct current characteristics or load conditio-ns are maintained. It is also contemplated to make each. line jack serve as a safety switch by pro- -viding each cabinet with a dummy plug, constructed entirely of insulating material, which may be thrust by a workman into the jack in the event that shutting off of the power is desirable,
as in case of an accident, without the necessity of running to a sometimes remote main disconnecting switch.
Having thus described my invention in detail, what I claim as new and desire to secure by Letters Patent, is:
l. A line jack of the character described comprising a base plate, support means mounted on said base, a pair of adjacently positioned approximately U-shaped contactors carried by said support means and each having a contact portion and an integral divergently related support arm, said arms slidingly engaging said support means, and means engaging said arms for yieldingly holding said contact portions in separable engagement.
2. A line jack of the character described comprising a base plate, support means mounted on said base, a pair of adjacently positioned approximately U-shaped contactors carried by said support means and each having a contact portion and an integral divergently related support arm,
-said arms slidingly engaging said support means,
and means engaging said arms for yieldingly holding said contact portions in separable engagement, said arms being free for limited' pivotal movement with respect to the support means at any stage of its slidable movement thereon.
3. A line jack oi the character described comprising a supporting base, guide pins mounted on said base, a pair of adjacently positioned approximately U-shaped contactors each having a contact portion and an integral divergently related support arm, said arms having sliding engagement with said guide pins, and means engaging said cross arms for yieldingly holding said contact portions in separable engagement.
4. A line jack of the character described comprising a base, guide pins fixedly supported by said base, a pair of adiacently positioned approximately U-shaped contactors each having a contact portion and an integral divergently related support arm, said support arms having openings to receive said guide pins, said openings being of suicient size to permit limited pivotal movement of said arms with respect to said pins, and means engaging said arms for yieldingly holding said contact portions in separable engagement.
5. A line jack of the character described comprising a base plate, support means mounted on said base, a pair of adjacently positioned approximately U-shaped contactors carried by said support means and each having a contact portion and an integral divergently related support arm. said arms slidingly engaging said support means, posts mounted in said base adjacent the Contact jaws, and springs interposed between said po-sts and said jaws.
6. A line jack of the character described cornprising a base, guide pins fixedly supported by said base, a pair of adjacently positioned approximately U-shaped contactors each having a contact portion and an integral divergently related support arm, each support arm having openings to slidingly receive said guide pins, said openings being of .suflicient diameter to permit limited