US2166323A

US2166323A - Control apparatus

Info

Publication number: US2166323A
Application number: US84801A
Authority: US
Inventors: Estel C Raney
Original assignee: Ranco Inc
Current assignee: Robertshaw US Holding Corp
Priority date: 1936-06-12
Filing date: 1936-06-12
Publication date: 1939-07-18
Anticipated expiration: 1956-07-18

Description

July 18, 1939. E. c. RANEY CONTROL APPARATUS Filed June 12, 1936 2 Sheets-Sheet 1 MOTOR ens/Iva INVENTOR BY W nfwifi ATTOR EY July 18, 1939. E. c. RANEY CONTROL APPARATUS Filed June 12, 1936 2 Sheets-Sheet 2 #1 ZZZ 3 F H 2 W.- N m m r 7 5 M M 2 92 I l. m 9 M 2 W R 5 m 4 w p O. J 5 i E T {k4 H 3 A 3 r d-l M 2 N a Patented July 18, 1939 PATENT OFFICE 2,166,323 oon'rnor. APPARATUS Estel C. Raney, Columbus, Ohio, assignon to Ranco Incorporated, Columbus, Ohio, a corporation of Ohio Application June 12, 1936, Serial No. 84,801

' 2 Claims. (o1.172- -2'z9) My present invention relates to electrical control circuits, and. more particularly to control circuits for electric motors including a protective device.

An object of my invention is to provide a protective circuit for a motor that will'function in the event of abnormal conditions such as when a winding is not cut out of the circuit or when the motor becomes overheated due to any condition, such as an overload during normal operating periods.

Another object is to provide a circuit including a protective device that is responsive to electrical heating means during the starting period of the motor and responsive to motor temperature during running periods of the motor.

In the drawings:

Fig. 1 shows a diagrammatic view of a motor and control circuits therefor, and shows, in cross section, a protective device connected in the circuit;

Fig. 2 is a simplified wiring diagram of Fig. 1; and

Fig. 3 is a simplified wiring diagram showing the protector applied to a different type motor.

The specific design and construction details of the switch or protective device utilized in my present invention is more fully explained in my copending application, Serial Number 84,800, now U. S. Patent No. 2,133,400.

The switch shown at 20 is a simple thermal responsive device, which has fixed and movable contacts 21 and 28, respectively. The contact 23 is fixed to the spring member 3| which normally tends to separate the contacts. The member 3| is fixedly mounted on the support-plate 38. A dog or lever 41 is used to engage the contact member 3| to keep it in the closed position during normal operation. The dog rests on the lever 3| at one end and on the ratchet 46 at the other end. The ratchet 46 forms a bearing point for the dog in the set position as a spring 48 supplies a downward pull to keep the contacts closed through the associated lever mechanism.

The ratchet 46 is capable of rotation on a pinion, (not shown) but is fixed in one position by a low-melting point solder, disposed between the ratchet 4B and the pinion. A heating coil 39 of resistance wire, is disposed within the pinion and is capable on definite periods of heating or during the passage of an overload current therethrough, of radiating sufficient heat to fuse the solder and allowing the ratchet to turn in a clockwise direction, due to the pull of lever 41 as supplied by the spring 48. When the ratchet 46 rotates, it displaces the lever 41 which automatically relieves the downward pull of the lever 41 on the contact member 3|, thereby allowing separation of the contacts tobreak the circuit. When the circuit is broken, the heating coil ceases to function and after a period of time the solder rehardens to again engage the ratchet.

At this time, the lever 49 may be operated to reset the switch.

The drawings also show a diagrammatic view l i of a motor circuit including a single phase AC induction motor 2| having a running winding 43 and a starting winding 31.

Electrical energy for the circuit is supplied by the

power lines

23 and 25. The line 25 is con- 15 nected directly to the running winding and to the starting winding 31. Current from wire 23 leads to the switch 20 and traverses the fixed contact 21, the movable contact 29, and the resilient member 3| at which point, during the starting operation, the path of the current is divided in two directions. Part of the current goes through the support-plate 38 of the switch 20 and through the heating coil or resistance 39. This coil 39 is spot-welded to the plate 38, to 3.3 insure electrical contact. From the coil 39, current passes through wire 4|, to the running winding 45.

During starting, the other part of the current goes directly from the support-plate 38, through the wire 32, to the movable contact 34 of a centrifugal switch 33. The contact 34 in the stopped position of the motor 2| engages the fixed contact 35 so that a circuit is made through wire 36 to the starting winding 31. 3.3

By energizing the starting winding 31 and the running winding 45 simultaneously, the field flux is thrown out of phase, to cause a rotating field. This causes the armature, or rotor, of the motor to turn. As the armature gains suificient speed, the arms of the usual type centrifugal switch, as designated at 33, move-outwardly from the rotor shaft. When the arins of the centrifugal switch 33 are sufliciently expanded, the circuit through the fixed contact 35 and the movable contact 34 is broken. This, of course, breaks the circuit through the starting winding .31. The winding 31 is no longer needed, since the motor is rotating and, in fact, if the winding 31 is allowed to remain in the circuit, it will cause overheating or a burnout.

As the contact 34 separates from the contact 35, it immediately makes contact with the other side of the switch, namely contact 43. Contact 43 is connected by wire 42 to wire 4| which leads b5 from the heating coil 39. It will be noted, therefore, that the heating coil 39 is now shunted out of the circuit, since the current traversing the support-plate 38 passes through wire 32, movable contact 34, fixed contact 43, wire 42, to the wire 4|, which is the path of least resistance. When the coil 39 is shunted out of the circuit, its heating effect is automatically stopped.

The coil 39 is in heating proximity to the soldered mounting of the ratchet 46. If for any reason the starting winding remains inthe circuit for too long a period, current flowing therethrough will fuse the solder. The ratchet 46 is then freed from its soldered engagement with its pinion and rotates in a clockwise direction,

as caused by the downward pull of lever 41,

through the tension of spring 48. This allows the

contacts

21 and 29 to separate to break the main circuit. In other words, if the coil 39 is not cut out of the circuit within a predetermined time period, the switch 20 will be actuated to break the circuit.

During the running period of the motor, when the starting winding is properly cut out of the circuit by the centrifugal switch 33, it is possible that too heavy a load may be placed on the motor, or too high a current may traverse the running winding 45. In any of these exigencies, the motor windings will tend to overheat. To protect the motor against overheating of this type, the switch 20 is mounted on the motor for example, within an end bell 50 of the motor (not shown), so that it is in heat-conducting proximity to the motor windings. In this manner, it will be seen that if the motor overheats, due to any of the aforementioned reasons, the solder will be heated to its fusing temperature practically simultaneously with the rise in temperature of the motor, and when the solder fuses, the ratchet 46 will rotate, causing separation of the contacts 2'! and 29. The switch 20 should be set to open at a safe temperature to prevent injury to the motor insulation.

The coil 39 will again become thermally operative should a load be impressed on the motor sufficient to slow it down to a point that the starting winding 31 would again be cut in by the centrifugal switch 33, to make the coil 39 operative to protect the motor.

The lever 49 protrudes to the exterior of the end bell 50 so as to be accessible from the outside thereof and thus provides a manual reset for the switch in the event it has operated. However, the switch 20 cannot be reset through the lever 49 when it is once operated until the temperature of the solder reaches the hardening point. This provides positive protection for the motor, for even if the lever 49 is wedged into the reset position, the rotating ratchet 46 will not allow closure of the contact members, if the solder is soft.

The same type of switch as 20 may be applied to a motor having continuously energized field winding or windings, for example, a repulsioninduction motor, shown in Fig. 3. In such a wiring system there is no starting winding to be cut out of the circuit, but a centrifugal switch 33 is again used to shunt the heating coil 39 as in the starting winding type of motor, as previously described. The switch 29 protects the motor against too heavy loads, too slow a start. overload currents, etc., because the wiring circuit is identical, except that the starting winding 31 is eliminated. In such a motor, the centrifugal switch is utilized -to shift contact 34, to provide a shunt path around the heating coil 39.

From the foregoing description, it may be noted that I have provided a switch to take care of any emergency that may arise in a motor circuit, during starting and running operations. The switch described is small and easily installed on the inside of a motor casing, with only the reset lever 49 extending through the casing. Preferably the switch is mounted on the interior of an end bell of the motor where it is subjected to the heat of the motor and the outer end of lever 49 extends to the exterior of the motor through a hole in the end bell. The switch provides a resetting control that not only protects the starting winding and the motor during starting operations, but also provides complete protection to the windings, should an overload of any type occur during normal operation.

While the forms of embodiment of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim:

1. In combination with a motor having a starting winding and a running winding, of a protector for the motor including a. circuit breaker connected in series with both of said windings,

electrically energized means for actuating the circuit breaker and connected in series with the running winding, said running winding and electrically energized means being in parallel circuit relation with the starting winding, and.

means responsive to normal operation of the motor for causing deenergization of the starting winding and said electrically energized means and responsive to abnormal operation of the motor for causing energization of the starting winding and the said electrically energized means.

2. In combination with a motor having a starting winding and a running winding, of a protector for the motor including a thermally actuated circuit breaker connected in series with both of said windings, said thermally actuated circuit breaker being disposed in intimate heat exchange relation with the motor and actuated upon excessive heating of the motor, said thermally actuated circuit breaker including electrically energized heating means for actuating the circuit breaker, said heating means being connected in series with the running winding and said running winding and heating means being in parallel circuit relation with the starting winding, and means responsive to normal running of the motor for causing deenergization of the starting winding and said electrically energized means and responsive to abnormal operation of the motor for causing energization of the starting winding and the heating means.

ESTEL C. RANEY.