US2475038A - Motor starting and safety switch - Google Patents

Description

July 5, 1949. A. R. LUCAS MOTOR STARTING AND SAFETY SWITCH Filed Sept. 28, 1946 lllllllllllllllllllllllllllllll 1' INVENTOR.

A/ffea A? Lama BY M M arraE'NEZS Patented July 5, 1949 REISSUED MOTOR STARTING AND SAFETY SWITCH Alfred B. Lucas, Gallon, Ohio Application September 28, 1946, Serial No. 700,074

4 Claims.

The present invention relates to electric switches and more specifically to switches through which current is supplied to motors first to the starting windings and then the running windings.

Among the objects of the invention is a switch provided with means for dividing the initial current between the two motor windings and subsequently breaking the circuit through the starting winding,

Another object is a switch provided with means for breaking the motor circuit under conditions of overload or excessive heating.

Still another object is a switch which automatically restarts the motor when the objectionable condition has been relieved.

ther objects and advantages will readily occur to those skilled in the art upon reference to the following description and the accompany ing drawings in which Fig. l is a top plan view of the switch elements.

Fig. 2 is a side view thereof and also shows diagrammatically the motor connections.

Fig. 3 is a view similar to Fig. 2 but shows in addition, diagrammatically, means for controlling the timing of the re-start.

Fig. s is a fragmentary section showing the switch of Fig. 3 in open position.

As shown in the drawing, the switch consists of a base or housing ill of insulating material relatively long and having at one end anchorage means i l for a pair of spring arms I 2, one on each side of but not in contact with, an arm I3 of bimetalfwhich extends through and projects from the endwall of the member I, the projecting end serving as connecting means for a lead wire It,

The free end of arm i3 carries a contact Hill exposed on both upper and lower faces oi the arm, while the arm itself is considerably shorter than the spring arms I 2. The spring arms 62 are fixed at their free ends to a conducting cross member IZA which carries a contact [23 exposed on both upper and lower faces of the member IZA.

Located in the end or" the base ill is a short conductor IS the inner end of which carries a contact I 5A in position to onset with the contact "B and to the outer end of which is connected a lead wire I ii.

In the bottom of the base i0 is another fixed contact ll mounted on a conductor IIA leading from the base or housing and to which is connected a lead wire l8. This contact I1 is below and in position to coact with the contact ISA carried'by the bi-metal arm IS. The housin III 2 also carries stop members IDA and IOB opposite respectively the contacts ISA and HE.

Mounted between the free end of arm l3 and; the cross member A, is a curved flat spring member 20, this being reversely curved at its ends to form sockets and being made of light spring material. Also extending between the same parts is a flexible lead wire 2 t.

In the use of the switch described above, the lead wire It is connected to one end of the rim-= ning winding A of a motor while the other end. winding A. is connected to one end of the starting winding and at their junction they are connected to a power supply or return line C. The con ductor it is directly connected to or is a part of the other power lead D. The conductor iii leads to the other end, or end opposite the running winding, of the starting winding B.

When the power leads C and D are not energized and no current is flowing through the switch, the parts are in the position shown in full lines in Fig. 2. When the current is turned on, the flow from lead (1 will be to the bl-metal arm it and from this it will be divided and part will go to contact ill and part through member 28 and flexible lead 2!! to contact WA, so that from lead D the flow of current will be through both the starting winding B and running winding A, all of the current traversing the bl metal arm It.

As a consequence, the arm it will be heated rather quickly and the contact of i 3A with l i will soon be broken. The time, of course, may readily be pro-set by using the proper strip for arm it.

With separation of contacts i321 and H, current flow will continue through contacts HE, MA, lead it and windings The heating effeet on arm it will be at the same time reduced, so that, under usual running conditions, the arm It will not move up sufiiciently to break the run-- ning circuit.

When, however, an overload occurs, and with it an excessive current flow, the arm is will move further and. cause the toggle spring 20 to snap over center and separate contacts E23 and ISA, as indicated in Fig. 4, and this condition will continue until arm it cools sufiiciently to move down and cause the toggle spring 20 to again thrust the latter contacts together.

While it may not be necessary in most cases to delay the re-start for a greater time than that of the natural cooling of arm l3, this time may be prolounged by such means as is shown in Fig. 3. In this figure, the stops IDA and IOB are shown as contacts NBA and HUB connected respectively to leads HI and 2, the former leading to a variable resistance device HA and the latter to any suitable device DD for utilizin the current. This arrangement provides for continuing the current flow through arm l3 when the parts are in the position of Fig. 4 and so continues the heating of the arm. It is of course to be understood that the current flow through leads Ill and H2 will be so regulated that the arm 13 will be allowed to cool at such rate as will produce the time lag desiredy I claim:

1. A motor starting and safety switch consisting of a suitable enlongated base having adjacent one end thereof a stationary contact adapted to be connected to the running windings of a motor and a second stationary contact adapted to be connected to the starting windings of said motor, a spring arm fixed to the other end of said base and carrying a contact at its free end, adapted to co-act with the first mentioned stationary contact to complete the running circuit, a second arm fixed to said other end of said base and carrying at its free end a contact adapted to co-act with the second stationary contact to complete the starting circuit through said motor, said secnd arm being connected to a source of current supply and being of bi-metal adapted to flex when heated, said second arm when unheated having its contact in circuit closing relation with the second stationary contact, a flexibl conductor fixed to said bi-metal arm and to the contact carried by said spring armyand a spring toggle member between said bi-metal arm and said spring arm and adapted to move said spring arm and contact away from its co-acting stationary contact when the bi-metal is undul flexed due to excessive'heating.

2. A motor starting and safety switch consisting of a base member, a spring arm fixed thereto and carrying a contact at its free end, a fixed contact normally touching the first contact, a second conducting arm adapted to flex when heated fixed to said base and arranged in generally parallel relation to the spring arm said second arm having a contact adjacent its free end, a fixed contact which the contact on said second arm touches when cold, a toggle spring cooperating with the free ends of said arms and arranged to press together the contact on said spring arm and its cooperating fixed contact when said second arm is subjected to normal heating and normal flexing and to separate the spring arm contact and its fixed contact when the second arm is subjected to abnormal heating and thereby abnormal flexing.

3. An electric switch consisting of an elongated base having flxed at one end thereof a spring arm and a bi-metallic conducting arm generally parallel therewith, means for connecting said bimetallic arm to a current source, a contact fixed to the free end of each arm, a pair of stationary {contacts fixed to saidbase and adapted to coact with respective arm carried contacts, and to lie in circuit closing position when cold, said bimetal arm adapted to flex when heated by passage of current therethrough and thereby separate its contact from its co-acting fixed contact, and a spring toggle member acting between said bi-m'etal arm and said spring arm and adapted to separate the spring arm carried contact from its co-acting 'flxed contact when through excessive heating said bi-metal .arm is unduly flexed.

4. A motor control electric switch consisting of an elongated base having fixed at one end thereof a spring arm and a bi-metallic conducting arm generally parallel therewith, means for connecting said bi-metallic arm to a current source, a contact fixed to the free end of each arm, a pair of stationar contacts flxed to said base and adapted to coact with respective arm-carried contacts in circuit closing position when said bimetal arm is cold, means for connecting the fixed contact coacting with the spring arm carried contact to the motor, said bi-metal arm adapted to flex when heated by passage of current therethrough and thereby separate its contact from its coacting fixed contact, a spring toggle member acting between said arms to maintain under normal heating the circuit closed relation of the contact on said spring arm and its coacting fixed contact and to separate the latter under abnormal heating, a second pair of fixed contacts with which the arm carried contacts are adapted to coact when said arm has been moved due to excessive heating, at least one of said second pair of fixed contacts being connected in a circuit other than the motor circuit and to thereby increase the cooling time for said bi-metal arm.

ALFRED R. LUCAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Obszarny June 19, 1945

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