US 2655576 A
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Description (OCR text may contain errors)
Oct, 13, 1953 w. G. MILNE ET AL 2,655,576
' DROP OUT FUSE SWITCH Filed April 15, 1953 Fir .1 56
Patented Oct. 13, 1953 2,655,576 DROP u FUSE SWITCH Winford G. Milne, Hamilton, Ontario, and Reginald E. Jones, Toronto, Ontario, Canada, assignors to N. Slater Company Limited, JHamilton, Ontario, Canada Application April 15, 1953, Serial .No. 349,074 6 Claims. (01. 200 114) This invention relatesto drop outfuseswitches.
As is known, such switches are used for disconnecting transformers or local circuits, from a main power feed.
Usually, such a switch essentially consists of an insulated upper contact to which the 'feed wire is attached, and an insulated lower contact'to which the transformer or secondary circuit is attached, a fuse serving electrically to connect the upper and lower contacts. The fuse isenclosed in a rigid insulating tube. The tube, with the fuse enclosed therein, in effect forms a switch member which electrically connects the two contacts. Upon an overload occurring in the circuit, the fuse burns out and the tube dropsdown, describing an arc of roughly 180. When the switch member has swung dowmaspreviously-described, it is manually removed and the blown fuse replaced by a new one inserted intothe tube, and the switch member returned to operative posi- VVhen the switch member is manipulated to break the circuit, the member very often draws a most destructive are which not only is injurious to the switch itself, but will sometimes spread to adjacent switches mounted in its proximity.
The main object of this invention, therefore, is to provide a switch of the type hereinbefore described, which can be opened manually without danger or hazards of drawing a destructive are.
In the drawing:
Figure 1 is a front view of the drop out fuse switch in circuit closed position. Figure 2 is'an elevation of the lower portion of the assembly of Figure l.
Referring now by numerals to the drawing, there are shown two conventional insulators, l0 and H, suspended by a conventional cross arm (not shown) by means of a conventional supporting bracket B (shown in part only) Supported. by the upper end of the insulator I0 is a resilient contact bracket I2, which takes the form of relatively stifi round wire in two identical parallel spaced strands (secondstrand not shown). The contact bracket is supportedby a lug 3 rigidly extending from one complementary element of a two-piece clamp 20. The contact bracket is secured to the lug l3 as by a clamping member [4 bolted to the lug, and is electrically connected to a lead (not shown) by a conventional connector I 6. The outer or free .end of each strand of the contact bracket is formed with an offset or arched portion ll terminating in divergent horns l8. w
Suspended from the lower end of the insulator H is a hinge bracket 2|. The hinge bracket is Secured by a bolt 24 to a lug 22 rigidly extending from one complementary element of a twopiece clamp 23. The hinge bracket 2! and the contact bracket I2 aforesaid also have associated with them the two terminals of the switch. The switch proper (more specifically to be referred to later), serves to complete the circuit between the two terminals.
The switch proper, shown as 3SA, includes a crank presenting two angularly-disposed legs or levers 28 and 21, and pivots 28 journalled in the hinge bracket 21 so that the crank is mounted for rotary movement on the axis of the pivots. The leg 21 carries astud 29 on which is threaded a nut 30.
Such a switch includes a fuse comprising a tube 3|, made of a tough insulating material, usually Bakelite, carryin'ga topcontact member 34 having a U-shaped lug 33 adapted electrically to engage the arcuate portions I! of the contact bracket 12. The lower end of the tube carries a clamp 36, one end of which is pivotally connected to the upper end of the leg 26 as by a pin 31.
Enclosed within the tube 3| is a fusible element (not shown) interposed between an upper pigtail (not shown) electrically connected to the "top contact member 33, and a lower pigtail 38 which projects through the lower end of the tube 3| and is electrically connected to the leg 21 of the crank by being clamped between the leg 27 and the nut 30. Thus, when the switch proper is closed, the circuit between the resilient contact bracket 12 and the hinge bracket 2| is closed.
The arrangement of clamp 36, and crank, the leg 21 of which is in efiect tied to the tube-3l (more particularly, being tied to the lower pigtail 38) is such that the tube is retained in its normal or circuit-closing position, as shown in Figure 1. When an overload occurs in the circuit, the fusible element blows out. This allows the lower pigtail 38 to dropbeing aided by the i volume of hot gas generated withinthe tube 3l- "hinge bracket 2|, bodily to lower the tube and allowing the crank to rotate clockwise on the cause the disengagement of thecontact 33 from the contact bracket [2. The tube will swing outwardly in an arc of a circle, and hang vertically from the hinge bracket. The blown-out or expended switch proper or fuse issubsequently removed and replaced'by a new one.
' The arched portion ll of the contact bracket 12 is so formed'that when the switch is closed as in Figure 1, the bracket is retained in such posi 3 tion, until the fuse blows out Or the switch is opened manually.
Conveniently, the tube 31 carries an eye 39 by which the fuse, when hanging from the hinge bracket 2|, may be swung upwardly into closed position as by a suitable insulated pole (not shown). Such tube, more particularly the clamp contact 36, carries a rigid lever or lug 4! to assist in the manipulation of the switch from the ground by the insulated pole.
The drop out fuse switch thus far described is a conventional one, and no claim is made thereto. 7
Such a switch serves not only as a fuse, but as a switch properly speaking, that is, a switch which is to be opened and closed as desired, to make and break the circuit between the switch terminals. When the switch is being opened, as already stated, the switch member often draws a most destructive arc. On the other hand, a switch according to this invention, now to be described, prevents the occurrence of any substantial or injurious arc.
Extending from the cl mp 3t, a portion 42, conveniently of a rectangular cross section. The portion 42 is so directed relatively to the clamp 36 as to be more or less generally parallel with the axis of the tube (ii.
Secured to the portion 42, as by a suitable twopiece clamp i l, is a resilient or flexible contact C. The contact preferably takes the form of four thin metal bars or leaves. Two such bars or leaves E and iel-l of unequal length, are disposed cn one side of the portion 52, while the other two bars or leaves and A, also of unequal length, are disposed on the opposite side of the portion :32. The upper or free end of the bar QSA is preferably provided with a rounded contact head 31'. 12 structure comprising these bars is essentially the equivalent of a multiple leaf spring, the two pairs of leaves being spaced apart except for a tip engagement between the longer member of one pair with the shorter member of the other pair.
A flexible contact arm C made as shown, that is, comprising four separate members, or two pairs, has many advantages. Such members generate friction, such generated friction tending to reduce resonant vibrations which will often occur when the contact is exposed to winds of high velocity and conceivably might cause the upper end of the switch contact to come into contact with parts of the switch.
Disposed to lie in the path of spring contact C, more particularly in the path of the end portion or head 4-? of the contact arm C, is a latching device. Ihe latching device may take the form shown, that is a lever 52 is pivotally suspended as by pin 5-1 from a pair of spaced parallel lugs 48 rigidly extending from one end of one complementary element of a two-piece clamping device so clamped to the contact bracket 2 as by a bolt The outer ends of the lugs d2 are each provided with down-turned lips or stops 5%, forming abutments or shoulders adapted to be engaged by the iatcl lever to determine or limit its anti-clockwise rotation as seen in Figure 1. The lever on the other hand, is free to rotate clockwise. Thus, as the contact C swings downwardly (clockwise) with the tube 3! it engages the levcr 52 of the latching device and is restrained from further movement until the switch contact C (more particularly its member 53A) has flexed sumciently to slide over and be released from the lever 52. The arrangement is such that before the contact C is free of the latch or lever 52, the fuse, more particularly the contact 33 of the fuse, is out of contact with the bracket [2 and is sufiiciently spaced therefrom to prevent arcing between the bracket 12 and the fuse contact member 33. The arrangement is also such that when the fuse is rotated anticlockwise, again to make or close the circuit, the contact arm C moves or swings the latch out of its path, whereupon electrical contact is made with the bracket I2, when the part A! will have cleared the latch or lever 52, and the latter having dropped by gravity anti-clockwise in to contact with the stops or shoulders 56.
1. In a drop out fuse switch of the kind described including a resilient contact bracket and a hinge bracket forming the terminals of the switch, a switch arm comprising an insulating tube, a top contact member carried by said tube for electrical engagement with said resilient contact bracket, a crank pivotally supported by said hinge bracket, a conductor including a fusible element within said tube electrically connected between said top contact member and said crank, aclamp carried by said tube and having a portion pivotally supported by said crank, the arrangement being such that said switch arm drops and swings open to break the circuit between the terminals when said fusible element blows out under an overload; the improvement comprising, spring conductor means secured to a conductor member associated with said tube bodily to move therewith, a latching device electrically connected to said resilient contact bracket and lying in the path of said spring means to be engaged thereby as said tube is swung toward circuitbreaking position and to retain said engagement until the circuit has been effectively broken between said terminals of the switch, said latching device operating to permit unimpeded return of said spring means with said tube to circuitmaking position.
2. In a drop out fuse switch of the kind described including a resilient contact bracket and a hinge bracket forming the terminals of the switch, a switch arm comprising an insulating tube, a top contact member carried by said tube for electrical engagement with said resilient contact bracket, a crank pivotally supported by said hinge bracket, a conductor incu a fusible element within said tube electrically onnected between said top contact member and said crank, a clamp carried by said tube and having a portion pivotally supported by said crank, the arrangement being such that said SwlLCh arm drops and swings open to break the circuit between the terminals when said fusible element blows out under an overload; the improvement comprising, a resilient flexible contact arm secured at its lower end to a portion of said clamp and rising in spaced relationship to said tube bodily to move therewith, a latching device electrically connected to said resilient contact bracket and lying in the path of the free end of said resilient flexible contact arm to be engaged by said free end as said tube is swung toward circuitbreaking position and to retain said free end in contact therewith until the circuit has been effectively broken, between said terminals of the switch, said latch operating to permit unimpeded return of said arm with said tube to circuitmaking position.
3. A drop out fuse switch as in claim 2, said resilient flexible contact arm comprising a leaf spring having an upper portion for engagement with said latching device and a plurality of tensioned leaf springs of unequal lengths effectively retaining said first leaf spring in flexed tensioned condition.
4. A drop out fuse switch as in claim 2, the resilient flexible contact arm comprising a pair of leaf springs of unequal lengths, the longer of said leaf springs having an upper portion for engagement with said latching device, and a second pair of tensioned leaf springs of unequal lengths for effectively retaining said first pair of leaf springs in flexed tensioned condition, the longer leaf spring of said second pair tensionally engaging the shorter leaf spring of said first pair.
5. A drop out switch as in claim 2, the resilient flexible contact arm comprising a pair of leaf springs of unequal lengths, the longer of said leaf springs having an upper portion for engagement with said latching device and a second pair of tensioned leaf springs of unequal lengths for effectively retaining said first pair of leaf springs in flexed tensioned condition, the tip of the longer leaf spring of said second pair tensionally engaging the shorter leaf spring of said first pair, said pairs being wholly spaced apart except for said engagement of said tip.
6. A drop out fuse switch as in claim 2, the re silient flexible contact arm comprising two leaf springs of unequal lengths, the longer of said springs having an upper portion for engagement with said latching device, the tip of the shorter of said springs tensionally engaging the longer of said springs, said springs being wholly spaced apart except for said engagement of said tip.
WINFORD G. MILNE. REGINALD E. JONES.
No references cited.