US771014A - Safety-switch. - Google Patents

Description

No. 771,014. -PATENTED SEPT. 27, 1904..

' G HILL. SAFETY SWITCH.

APPLICATION FILED SEPT.27, 1902. N0 MODEL.

. 554 4/ v Line-002s 2Q 62 M Su-ucntoz Patented September 27, 1904.

UNITED STATES PATENT OFFICE.

TO MICHAEL JOSEPH DOHERTY, OF MONTREAL, CANADA.

SAFETY-SWITCH.

SPECIFICATION forming part of Letters Patent No. 771,014, dated September 2'7, 1904.

Application filed September 27, 1902. Serial No. 125,132. (No model.)

To all whom, it may concern:

Be it known that I, GEORGE HAGAR HILL, of the city of Montreal, in the district of Montreal and Province of Quebec, Canada, have invented certain new and useful Improvements in Safety-Switches; and I do hereby declare that the following is a full, clear, and

exact description of the same.

My invention has for its object to provide a highly-sensitive electrical safety-switch and one wherein the most sensitive parts will be cut out during abnormal conditions.

The invention may be said, briefly, to consist in providing, in combination with a switcharm adapted to fall by gravity, means for supporting said switch-arm consisting of an electrically-operated detent, an amperage-coil and a voltage-coil 'iri the circuit to be protected, a pair of branches from said main circuit and leading from each side thereof to ground, said brancheseach including a coil and said coils being wound together to constitute a solenoid, while each of said branches also includes the coil of an electromagnet. A pair of bridges lead from a portion of the lines of these branches between the coils of said electromagnet and the coils of said solenoid to within close proximity of the lower ends of the cores of said magnets and are adapted to be attracted by said magnets and drawn into contact therewith, the opposite ends of said cores being connected electrically to the leads of the main circuit.

For full comprehension, however, of my invention reference must be had to the accompanying drawings, forming a part of this specification, in which similar reference characters indicate the same parts, and wherein Figure 1 is a plan view, partly in section, of a safety-switch constructed according to my invention. Fig. 2 is a longitudinal vertical sectional view taken on line A B, Fig. 1. Fig. 3 is a transverse sectional view taken through one of the blades of my improved switch on line C D, Fig. 2, and illustrating particularly the contact-faces between said switch-arm and the contact-terminal of the switch; and Fig. 4 is a diagrammatical view illustrating the wiring of my improved safety switch.

The switch-arm consists of a pair of blades 6 and 0, connected together by an insulated yoke d and pivoted to a pair of brackets a, all as usual. The switch-terminals f and g and it and i consist of blocks of conductor material having their outer faces beveled, as shown in Fig. 2, and serrated, as shown in Fig. 3, and similar blocks is are carried by the switchblades and have their bearingfaces m beveled and serrated correspondingly to bearing-faces of the terminals of the switch.

The yoke (Z of the switch-arm is perforated at its middle andhas a pin a projecting there through, with a disk 0 upon one end and a handle 19 upon the other, while an eXpansile helical spring q bears between the outer side of the yoke and said handle and normally maintains said handle yieldingly away from the switch-arm. A detent-lever 4", having a hooked end 5, is pivoted at its other end, as at t, to a portion of a bracket for supporting a solenoid, to be presently described. This lever has a downward projection 10 to project to apoint adjacent to the means for operating said detent-lever.

A pair of carbon-fingers 2 and 3, respectively, are carried by each blade of the switcharm and the outer terminals, the carbons 2 being rigidly secured to the switch-arm preferably by pins 4, and the carbons 3 being set in sockets in the switch-terminals f and h and yieldingly held in a position to project beyond said sockets by eXpansile springs 5 within the latter. The function of these carbons is to presentan arc while the switch is being opened. A single-coil solenoid 6 is supported in a bracket 7, (before mentioned-,) secured to the base 8 of the switch, and a second solenoid, comprising two coils 9 and 10, is supported in a bracket 11, secured to the base. Each of these solenoids has a laminated core slidable therein, the core 12 in the solenoid 6 being adapted to act directly upon the detent-lever GEORGE HAGAR HILL, OF MONTREAL, CANADA, ASSIGNOR OF ONE-HALF and the core 13 of the solenoid 9 and 10 acting upon the core 12. These cores are of similar construction, each consisting of a laminated main core-piece, having a disk 14: at its lower end and its upper end tapered, as at 15, a rod 16 resting freely upon the latter and projecting upwardly through the coils and having a head 17. A Ushaped bracket 18 is secured to the underside of each of the brackets 7 and 11, the upper bracket 18 serving as a guide for the disk upon the lower end of the upper core and for the head upon the rod resting upon the lower core, while the lower bracket 18 carries a sleeve 19, through which a screw 20 is threaded, said screw supporting the lower core. A pair of electromagnets 22 and 23, respectively, having cores 24 and 25, are located, preferably, at the lower end of the base and near each side thereof, and a pair of spring- contacts 26 and 27 are secured at one end to contact- pieces 28 and 28" upon the base of the switch, and the opposite end of each extends to within close proximity of the lower end of the cores 2% and 25, and they have armaturepieces 29 thereon. These armature-pieces are ad justabl y supported upon screws 30, threaded vertically through bracket-arms 31 upon the base.

The wiring of my improved safety-switch is as follows: The main leads 34 and 35 of the circuit are connected, respectively, to the switchterminals f and 71. A wire 36 is taken from switch-terminal 1 to the upper terminal of the coil 6 of the upper solenoid, the lower terminal of this coil being connected by a wire 37 to one end of a contact-piece 38, serving also as a means for supporting the electromagnet 22. A wire 39 leads from the opposite end of this contact-piece to the light branches 40, from which a wire 41 (broken to admit of the connection of a meter, as will be pointed out) leads to the lower end of a contact-piece 42, similar to the contact-piece 38 and supporting electromagnet 23, and a wire 43 connects the upper end of this last-mentioned contactpiece L2 to switch-terminal 2'. The upper ends of the coils of the electromagnets 22 and 23 are electrically connected to the contact- pieces 38 and 42, the lower end of the coil 22 being connected by a wire 4a to contact-piece 28, a wire 45 connecting said contact-piece to the upper terminal of coil 9, while a wire 46 connects the upper terminal of coil 10 to contactpiece 28, and the latter is connected by a wire 47 to the lower terminal of the coil of electromagnet 23. A wire 48 connects the two coils 9 and 10 to ground 4:9.

In order to economize current, I include the shunt-coil of the meter in the shunt-circuit of.

my improved safety-switch, thus enabling the resistance to be distributed through all the shunt-coils, including the shunt-coil of the meter, thereby making coarser wire to be available for the windings, and consequently a less delicate construction to be provided. As the meter itself forms no part of my invention and may be of any of the well-known types such as, for instance, the Scheeffer recording wattmeter-well known to the trade, I will not describe nor illustrate same in detail, but only indicate its coils in diagram in Fig. 4:. The series coil of the meter is, as usual, included in the lighting or other circuit being supplied and which in this instance is the circuit to be protected, wires 61 and 62 serving, as usual, for this connection, and are connected to the sides of the beforementioned break in line 41. To effect the economy just mentioned, I connect the usual terminal wires 65 and 66 of the shunt-coil 67 of the meter to the wire 62 of the series coil of the meter and upper terminal of coil 23, respectively, though said shunt-coil of the meter may be included in any other manner in the shunt-circuit of my improved safety-switch. The upper terminal of coil 22 is electrically connected to contact-piece 38.

The operation of my improved safety-switch is as follows: The switch is closed by lifting its arm by its handle 2) and pressing same into contact with the switch-terminals, the pin a being thereby pressed past the hooked end a of the dctent-lever '1', and upon the release of the handle the spring q will tend to force out the handle 7), thus causing the disk 0 to bear tightly upon said hooked end and draw the contact-blocks upon the switchblades tightly into contact with the terminals. Upon an overload of current in the circuit the solenoid 6 will be energized, its core 12 drawn up, thereby raising detent-lever 7' and releasing the switch-arm, which is caused by gravity to drop, the spring 5 during this release pushing out the carbon 3 and maintaining a contact until the switch-arms are sufliciently far from the switch-terminals to avoid an arc. The switch is thus opened, and simultaneously therewith one or both of the magnets 22 and 23 (provided a ground has been accidentally established in the circuit) will be energized, the armature 29 attracted, and an easy course to ground for the abnormal current provided from either or both of the wires 37 and 43 through contact- pieces 38 and 42, cores 24: and 25, contacts 26 and 27, coils 9 and 10, to ground through wire 18, which course will include less resistance than the lamps in the branch circuits, and therefore relieve the circuit to be protected of dangerous conditions attendant upon accidental grounding of the outside or local circuit or abnormal flow of current attendant or not with increased potentiality. The object of grounding the circuit simultaneously with the release of the switch is to free the circuit of abnormal current during the brief period while the switch is opening. Upon a rise in potential between the lines either or both of the coils 9 and 10 will be energized, core 13 lifted, and the detent-lever '1' raised through the medium of rod 16, disk 14, core 12,'and the rod 16 in the upper solenoid and its head 17, thus opening the switch. In order for the higher potentials to reach these coils 9 and 10, it will have been necessary that the magnets 22 and 23 be energized, which will have closed the bridges 26 and 27 and cut out the coils of said magnets, before pointed out,

thereby protecting the coils of said magnets.

IO The bridges are held open by gravity when normal conditions exist, and in positions variable according to the resistance it may be desired to make the switch overcome at this point before opening the circuit. For in- 5 stance, if the switch is applied to the'protection of a low-voltage current say fifty volts and it is required to work upon a rise in potentials to two hundred volts these bridges should be supported a greater distance from themagnets than if the switch were required 3 main circuit, and means whereby said switch is opened included in said branch circuit, a bridge connected at one end to a point in said branch circuit and the other end thereof being normally open and adapted to make connection with another point in said branch circuit,

adjustable means for retaining said open end of the bridge in variable adjacency to the last-mentionedpoint in the circuit, said means consisting of a movable stop upon which the 4 free end of said bridge rests, electrical means included in said branch circuit between said bridged points and adapted to close said bridge upon abnormal conditions occurring in said main circuit, for the purpose set forth.

'2. The combination with a main circuit to be protected, a branch circuit leading from said circuit to be protected, a switch included in said main circuit, and means whereby said switch is opened included in said branch circuit, a bridge connected at one end to a point in said branch circuit and the other end thereof being normally open and hanging below and adapted to make connection with another point in said branch circuit, adjustable means for retaining said open end of the bridge in variable adjacency to the last-mentioned point in the circuit, said means consisting of a vertically-movable stop upon which the free end of said bridge rests, electrical means included in said branch circuit between said bridged points and adapted to close said bridge upon abnormal conditions occurring in said main circuit, for the purpose set forth.

3. The combination with a circuit to be protected, a meter including a series coil and a shunt-coil for measuring the current flowing over said circuit, and aprotective circuit, of means for including said shunt-coil of the meter in said protective circuit, for the purpose set forth.

4. The combination with a circuit to be protected, a meter including a series coil and a shunt-coil for measuring the current flowing over said circuit, and a protective circuit in shunt with said circuit to be protected, of means for including said shunt-coil of the meter in said protective circuit, for the purpose set forth.

In testimony whereof I have aflixed my signature in presence of two witnesses.

GEORGE HAGAR HILL.

Witnesses:

WILLIAM P. MoFuA'r, FRED. J SEARs.

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