US1058296A - Combined potential and overload switch. - Google Patents

Description

- E. L. GALE, Sn. oomnmnn POTENTIAL AND OVBBLOAD SWITCH.

APPLICATION FILED JUNE 11, 1907.

1,058,296. PatentedApr. s, 1913.

STATES PATENT OFFICE.

ERNEST'L. GALE, 8B,, .01 YONKERS, NEW YDRK, ASSIGNOR T OTIS ELEVATOR COM- PANY, 0F JERSEY QITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

COM BINED POTENTIAL AND OVERLOAD SWITCH.

a citizen of the United States, residing at Yonkers, in the county of l/Vestchester and State of New York, have invented a new and useful Improvement in Combined Potential and. Overload Switches, of which the following is a specification.

My invention relates to improvements in electric switches in which the same is maintained in closed position by magnetic means and released upon excessive current flow or fall in'potential; and has for its object to providemeans for opening a switch by the heat generated by excessive current.

.Another object of the present invention is the provision of an automatic circuit-interrupter comprising a simple and inexpensive element which may easily be replaced.

A further object is to prevent or reduce to a minimum any destructive arcing or flaming at the contact where the circuit is interrupted.

Further objects of my invention will appear more fully hereinafter.

In the accompanying sheet of drawing, whiclr forms a part of this specification, Figure 1 is a front view of a preferred form of my invention in its closed position; Fig. 2 is a side view of Fig. 1; Figs. 3, 4 and 5 are modified detail parts of Figs. 1 .and 2; and Fig. 6 is a diagrammatic representationof a motor-controlling system embodying my invention.

Similar reference characters designate similar parts throughout the various views.

10 designates a substantial base which may be'of any desirable insulating material, such as slate or marble, upon which are mounted the various switch parts.

11 designates a knife blade contact element adapted when closed to place in intimate electrical connection the fixed contacts 13, 23 and 25. A similar knife blade contact element 12 performs a similar functiorr with regard to the three fixed contacts 14, 24 and .26. These knife blade contact members are rigidly mounted upon an insulation piece designated by the numeral 27. This latter piece 27 has also attached to it two brackets 31, 31 through which passes a in 32, the latter serving as a hinge bearing between the brackets 31, 31 and a fixed "bracket 33 which is rigidly mounted upon the insulating base 10.

Specification of Letters latent.

by the Patented Apr. 8, 1913.

Application flied June 11, 19,97, Serial No. 378,406.

28 designates a metallic piece firmlyconnected to the insulation 27 and it is preferably made of magnetic material. This piece 28 is arranged to cooperate with an electro-magnet 30, the core' of which is firmly bolted to the switch base 10. A handie 29, b which the switch members 11 and 12 are c osed, is mounted upon the metallic piece 28. r i

36 designates a spring-pressed detent and 37 is a spring, both of these are contained by the housing 38 which is firmly fastened to the switch base 10. The detent 36 is adapted to cooperate with the metallic piece 28 in such a way that when the knife contact members are in closed position, the detent 36 compresses the spring 37. The tendency of the sprin 37 is to open the Switch at all times and t e spring is' made sufficiently strong to cause the switch to open. The switch when closed, however, is prevented from opening by the magnetic attraction of the electro-magnet 30 when the latter is suf' ficiently energized by an electric current. The brackets 31, 31, are both provided with lips 34, 34 which cooperate with a pin 35, fastened to the bracket They are for th purpose of'limiting the movement of the switch when the same is in itsopen position.

Between the fixed contact blocks 21- 15 and 2216, where it is customary to place fuses, I provide a device which forms an important feature of my invention. This device, ofwhich there are preferably two, one for each pole, comprises a metallic piece 17 which has an apprecialiilc resistance and a high temperature of fusion, each end of which may be provided with a slotted terminal for convenience in fastening in place. resistance mcn'ibcr 17 is soldered, or otherwise fastened by some fusible alloy, :1 connector or binding post- 19 which isprovided with a screw connection at one end so as to facilitate the fastening of a wire thereto.

Fig. 3 shows an enlarged modification of the device designated by 17 and [8 in Figs. 1 and 2. The main features of difference arc in having slotted terminals 3!) and 40 and also in having the connection 19 fastened fusible alloy 43 to the resistance element- 17 at'an inclined position. A screw 41 and washers 42 are .rovided for wire connections. The object in having the con- At a proper point. on this metallic necti'on 19' at an angle to the resistance element 1'? is for the purpose of causing the former, upon becoming unsoldered due to end. A flat spring 44 engages this shoulder and exerts a pressure upon the connector 19, the tendency of which is to force the connector 19 away from the resistance element 17 should the solder joining them become plastic or fused. The spring 44 may be of any desired construction or form, although I prefer the construction as shown on the drawing, in which the spring 44 has a U-shapedcut-away portion 47 at one end for the purpose of engaging the shoulder 48, and is fastened at its other end to a small block 45 which in turn is fastened by the screws 46 to the switch base 10. The spring 44 might advantageously be stamped out of a single piece of material,

The wiring diagram depicted in Fig 6 shows one way in which my improved switch may be used in connection with a source of current supply and an electric motor, in conjunction with an electrically operated. brake. Its operation is as follows: Assuming the switch is manually closed by means of the handle 29, the electro-magnet 80, which receives current from the mains and through the connectors 19 and 20, willmaintain the switch in its closed position as long as there is sufficient potential in the main line circuit to prop crly energize it. Upon closing the switch the knife contact members 11 and 12 close a circuit to the motor-armature 50 through the wire 53, brush- 52, brush 51, starting resistance 58, and wires 57 and 56. A circuit is also closed to the shunt field 59.

through the wires 53 and 56. Atthe same time the magnet winding of the electric brake 49 receives current from the mains iand through the switch contacts 23 aind 24. The eii'ect of this is to release the bi'akc and allow the motor to start, the adjustable resistance 98 may be operated in any desired manner to properly start or control the motor. Should the potential in the main supply and drop beyond a certaih point, the electro-magnet 30 will become partially deie'nergized and the spring 37, (Fig. 2), will at once overpower the holding-in property of the magnet and thereby open the switch blades 11 and 12.

circuit to the motor is at once interrupted at the contact terminals 25 and 26. it the same time the circuit to the brake 49 is broken the contacts 23 and The brake is thereupon applied by a spring (not the retalning magnet 30 to be opened at these fused connections. The switch is thereupon opened and the motor brought to rest. It is the usual practice, where it is desired to make an electrical connection between a power circuit and some electric-a device, to place a double pole switch of some description which is provided. with fuses, either of an open or inclosed type. We will assume, for example, that such a switch connects an electric elevator system and a source of electrical supply, letit be further assumed that a heavily loaded elevator car is descending and the main line fuses blow-f due to excessive current or other causes.

The result is that the heavy descending load will drive the hoisting motor as an open circuited generator, current at an increased voltage will keep the brake from being applied, and the machine will run away with mor or less disastrous results. Or, should the main switch be provided with the ordinary type of no voltage release and the potential drops by an amount suificient to open the main switch, the brake, with which every electric elevator is supplied, will remain partially energized by the counterelectro-motive force due to the rotating ele vator motor and will remain inactive at just the time when'it should be applied to stop the elevator machinery. These objectionable features are ever present in the was usual type of so-called over-load and no voltage release switches, whether they be operated by magnetic or other means. A further objection to the usual type of over load switch when used in connection with an electric motor, is that the tripping device used thereon isset to operate at a certain overload. In the operation of electric motors especially, it is frequently desirable to overload the motor for a short space of time sometimes-as much as 50%. It would not be safe to set such a switch to operate at 50% overload for the reason that it would permit a 45% overload upon the motor for an indefinite time, which would most assuredly ruinv the motor. These and other objectionable features ever present in the prevailing type of overload and no voltage release switches, are entirely overcome by using such a switch as I have described in connection with the drawing annexed to this specification, and for the following reasons: In the first place it will be recalled that in the description of Fig. 6 the terminals of the electric brake 49 are connected to small terminals 23 and 24- on the switch, and it is clearly seen that should the switch be opened from any cause whatsoever, the releasing ma net of the electric brake 49 is imme iately open-circuited at both terminals and the brake is applied with maximum power, there being no possibility of the brake-releasin ma et remainin energized and the bra e he d ofi. Anot er feature to be found'in my improved switch is the property of allowing a certain overload to pass through the same to any desired electrical device for a short space of time without causing the switch to open its contacts; but, should'this overload continue beyonda certain period of time, the switch would at once operate This time element feature as a pl1ed to an overload switch I consider of t he greatest value, for, although the switch I have described will open its contacts whenever the main current rises to a redetermined amount for a certain lengt of time, it also permits of a I 'much greater flow of current for a short period only. This latter feature is very desirable in the operation of electric motors as applied to elevator service, although not confined to any one particular electrical device. The resistance member which I use to accomplish the openingof my switch upon an overload, is very simple andicheaply constructed. As before stated, it has an appreciable resistance whereby a current is enabled to heat it, but this resistance is so very low that the loss of energy therein is negligible and does not have to be taken into account. The length of this resistance member bears acert-ain relation to its'accuracy of operation owing to heat being conducted away by the terminals at either end. As soon as a resistance member has operated to open the switch it is only necessary to replace it with a similar one, and in the meanwhile the first one can be-resoldered and used again, or as many times as desired.

Without limiting myself to the precise fully realizing that many changes and addi tions may be made by those skilled in the art without departing from the spirit and scope of my invention, what I claim as novel and desire to protect by Letters Patent of the United States is:

1. The combination of an electric switch, an ele'ctro-responsive device controlling the switch and havin a circuit independent of the switch, and t ermostatic means in cir for controlling the operation 0 said electroresponsive device.

2. The combination with an electric switch and having an electric circuit independent of-the switch, and heat controlled means included in said circuit and dependent on the current flowing through the switch magnet.

3. The combination with a switch, of a conductor connected thereto and adapted to be connected to a source of current supply, an electro-magnet controlling said switc and a heat responsive device connecting the electric circuit of said electro-magnet to said conductor and operable upon arise in temperature of said conductor above a predetermined point to disrupt said circuit.

4. The combination with a two-pole switch, of conductors leading from a source of current supply, a holding electromagnet' having its winding in a circuit across said conductors for holding said switch closed during the passage of normal current, and a thermostatic devicenormally in circult with said magnet winding and operable upon the flow of excess current for a predetermined time to cause the openin of'said switch.

In testimony whereo I have signed my name to this specification in the presence of two subscribing witnesses.

I ERNEST'L. GALE,'SR.

W'itnesses:

ALFRED C. BECHET, Ennns'r L. GALE, Jr

form and construction herein described, and

cuit with said electro-responsive device and controlled by the current throu h the switch for controlling the operation of the electroswitch, of an electro-magnet controlling said

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