US2133400A - Control apparatus - Google Patents

Description

Oct. 18, 1938. E. C RANEY 2,133,400

CONTROL APPARATUS Filed June 12, 1936 2 Sheets-Sheet l INVENTOR w JP g iza 221:4

ATTORNEY Oct. 18, 1938. E. c. RANEY 2,133,400

CONTROL APPARATUS Filed June 12, 1936 2 Sheets-Sheet 2 +325 "as; I'

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ATTORNEY Patented Oct. 18, 1938 UNITED STATES CONTROL APPARATUS Estel C. Raney, Columbus, Ohio, assignor to Ranco Incorporated,

Application June 12,

4 Claims.

My present invention relates to electrical control circuits and controllers therefor and more particularly to thermally controlled circuits and thermally operated switches for such circuits.

An object of my invention is to provide an electric switch for the proteciion of motors. This switch is thermally actuated and has a plurality of heating coils disposed in proximity to the thermal element for operating the swiich under various conditions. The switch as designed, is also sensitive to' overheated conditions of the motor.

Another object is to provide a control circuit including a thermal switch having two heater elements for connection to, for example, a capacitor-start type of motor. One heater is to be in series with the running winding and the other heater is to be in series with the starting winding. The first heater protects the motor against 20 current overloads, etc., while the second heater protects against a stalled motor, or too heavy a load on the motor. The switch is to be mounted so that it is responsive to excessive motor temperatures.

A still further object is to provide a tripping device to be used in the construction of the switch which includes a freely translatable latch or dog for holding the switch in one position and a thermal release device associated with the latch; which device is responsive to emergency conditions of excessive temperature for releasing the latch to effect movement of the switch contact.

Other and further objects and advantages will be apparent from the following description, reference being had to the accompanying drawings wherein preferred forms of embodiments of the present invention are clearly shown.

In the drawings:

Fig. 1 is a side elevational view of the switch with the contacts in closed position;

Fig. 2 is a view, partly in section, of the opposite side of the switch shown in Fig. l, with the contacts in the open position;

Fig. 3 is a top view of the switch;

Fig. 4 is a sectional view on a larger scale, the section being taken through the ratchet and solder pot;

Fig. 5 is a view in elevation of the opposite side or the ratchet shown in Fig. 4, and

Fig. 6 is a schematic wiring diagram of the switch in a motor circuit.

Fig. 1 shows a thermally actuated switch 20. A base 2| fabricated from a dielectricmaterial, is used as a means to attach the switch to an a corporation of Ohio 1936, Serial No. 84,800

appliance, for example, within the end bell of a moior. A member 23 of pressed metal is positioned on the base 2| by two integral lugs 26' which pass through the base and are clinched over on the opposite side of the base 2|. The member 23 is also provided with an integral connecting lug 2'! for electrical connection. A fixed contact 22 of suitable material, such as silver, is mounted, as by riveting, on the support member 23.

A movable member 25 is preferably fabricated from spring material, such as full temper phosphor bronze, which has desirable electrical conducting properties. A contact 24 is mounted, as by riveting, to the movable member 25. The member 25 is so formed as to normally tend to separate the contacts.

The opposite end of the member 25 s con nected to the upper side of a U-shaped support plate 28 by lugs 29 which are integral with the plate 28 and pass through apertures 25 in the member 25. The lugs 29 are clinched over to insure a tight mechanical and electrical connection between the support 28 and the member 25.

The opposite or lower leg of the U-shaped support member 23 is fixed to the base 2| by integral lugs 30 which pass through the base 2| and are clinched over on the opposite side of the base 2|.

The member 28 also acts as the support for a ratchet 3|, through its associated parts. A hollow bearing post 32 forms the spindle for the ratchet 3|. The post 32 is provided with an outwardly extending flange 33 for connection to the support 28. The flange 33 is attached to the member 28 by integral lugs 34 clinched over to form a tight engagement.

The ratchet 3| loosely embraces, and can be freely rotatable on the post 32 when not held in place by solder. A substantially circular plate 35 is pressed over, and siaked to, the post 32 to prevent displacement of the ratchet 3|, with respect to the supporting post 32.

To prevent the ratchet 3| from normally being rotatable, a low mel ing point solder is used to solder the ratchet 3| to the post 32. The composition of this alloy 36 may be varied to obtain any desired fusing point, for example, 200 F.

An engaging means, or dog 31, oi dielectric material is employed to provide an actuating link between the ratchet 3| and the member 25. This dog is freely translatable, in that no fixed bearing point is provided. The dog 31 has a single'projection 33on one end thereof to engage with the teeth of theratchet 3|. The opposite end of the dog 31 is provided with two projections 39 and 42, that form a substantially forked end portion on the dog 31. The point 39 rests on the top of the member 25, as part of the dog passes through an opening 43 in the member 25. The other projection 42 is so disposed as to limit the upward movement of the dog 31 by engaging the underside of the member 23, as shown in Fig. 2; the base 2| being cut away, to form openings therethrough for the various extending parts of the dog 31.

The dog 31 is drawn normally toward the base 2| by the tension of a spring 40 attached at one end through the hole 44 in the dog 31, and at the other end to the reset guide member 4| which is fixed to the base'2l. The spring 40 is so disposed as to supply a horizontal component of force tending to force the dog 31 toward the ratchet 3| as well as provide the aforementioned downward tension. A reset lever 45 of pressed metal is pivotally attached to the dog 31 by a rivet pin 46. The lever 45 is split at its upper end to form a forked portion which engages either side of the dog 31. The opposite end of the lever 45 passes through an aperture -45 in the guide member 4|. This constructionis followed to assure alignment of the lever 45 and associated parts. The device 20 may be suitably secured to and on the inside of the end bell 60 of the motor 54 and the lever 45 projects through an opening 6| of the bell 60 so as to be accessible from the exterior of the motor for resetting of the tripping device.

It will be noted that when the projection 38 on the dog 31 is set in the teeth of ratchet 3|, I

the opposite end or projection 39 is bearing down on the spring contact member 25. In this position the spring 4|] is tending to draw the dog 31 downwardly, which firmly presses the contacts 22 and 24 together to make an electrical contact. This position may be studied in Fig. 1.

When the projection 38 on the dog 31 has been displaced from engagement with the teeth of the ratchet 3|, the spring pulls the dog 31 downwardly, until pin 46 rests on the base 2|, in which position the dog 31 pivots on the pin 46 due to the tension of spring 40: and the projection 39 raises, to allow separation of the contacts 22 and 2 4. The other projection 42 of the forked end of dog 31, limits the upward movement by engaging the contact support member 23. This position of the device is illustrated in Fig. 2.

The projection 42 acts as a bearing point against the member 23 when the "dog 31 is being reset. As the reset lever 45 is pressed inwardly the dog 31 pivots on the projection 42 as the projection 38 is raised relative to the base. The projection 38 contacts the teeth of the ratchet 3| but due to the translatable movement of the dog, is capable of slipping past the teeth until the lever 45 has reached its maximum inward movement. During this resetting operation the contacts 22 and 24 are not in engagement as the dog 31 is pivoting on its projection 42. As soon as the pressure is released on the lever 45, spring 40 supplies a downward tension to engage projection 38 with the teeth of ratchet 3| and also to close the contacts, since projection 39 of the dog 31 is now bearing down on the contact member 25.

From the foregoing it wil be noted that it is impossible to make contact through the device 20 by pressing in on the lever 45. In a like manner if the ratchet 3| is not fixed in position, that is, if the solder is fused, it is also impossible to close the switch 20.

' In the present embodiment two heating coils 41 and 48 of any desired resistant material are disposed. within the bearing post 32, in heattransferring relationship to the solder 36. One end of each of the coils 41 and 48 is spot-welded or otherwise attached to the support member 28. These coils 41 and 48 supply radiant heat when electrically energized by the passage of a current therethrough.

When either, or both of these resistances supply sufficient heat to bring the temperature of the ratchet 3| and solder 36, to say, 200 F., the solder 36 will fuse and the ratchet 3| will be capable of rotation on the post 32. In the set position of the switch, spring 40 and dog 31 are constantly supplying a downward pull, or turning torque, on the ratchet 3|. Therefore, when the solder 36 fuses, the ratchet 3| rotates in a clockwise direction and allows the dog 32 to come to the position as in Fig. 2. It is apparent that by varying the resistance of the coils that the time period for operation may be altered to give any desired time cycle.

The same effect may be obtained when the switch 20 is mounted on a motor. If the motor frame reaches a predetermined temperature of say 200 F. due to a heavy load, a scraping armature, etc., the switch 20 will be heated conductively by the motor frame, to fuse the solder 36, which'will allow rotation of the ratchet 3| to separate the contacts 22 and 24.

The points 22 and 24 are incapable of being reset after operation untiLthe solder 36 has rehardened. At this time, the reset lever 45 may be pressed inwardly to engage the dog projection 38 with the ratchet 3|, thus re-closing the contacts 22 and 24.

This particular feature of construction is a safety factor, for it will be noted that even when the lever 45 is held in the set position, that the contacts cannot be closed until the ratchet 3| is fixed in position. This assures that the motor 54 has cooled to a safe temperature before operation can be resumed.

Fig. 6 illustrates a schematic wiring diagram, showing one of the many circuits in which the switch 28 may be advantageously utilized. A single phase AC motor is generally indicated at 54, having a starting winding 53 and a running winding 52. Current is supplied by the power lines 50 and 5|; Line 5| is connected to both the starting winding 53 and the running winding 52. The other side of the line may be traced from wire 50, to contacts 22 and 24 of switch 20, through member 25, then splitting through heating coils 41 and 48. From the coil 48, the current goes through wire 51 to the field running winding 52, to complete the circuit. The current through coil 41 traverses wire 55, condenser 56, centrifugal switch 59, and wire 58 to complete the starting circuit. When both the running and starting winding circuits are energized, the motor starts to rotate. As the motor 54 gains speed, the starting winding 53 is no longer required and a usual type of centrifugal switch 59 opens the circuit, through the winding 53 and the heating coil 41.

In this particular embodiment, the resistance 41, which is placed in series with the starting winding, is so balanced with the resistance 48 that the two resistances 41 and 48 radiate sufficient heat to fuse the solder 36 in a predetermined time period. This will protect the winding if the motor should not start, or should not gain sumcient speed to cut the winding 53 out of the circult.

The resistance 48 in series with the running winding, is balanced to supply sufilcient heat to keep the switch at a temperature of say, F. (normal running temperature), during normal operation. Thus, if an overload current should pass through the coil 48 to cause a rise in temperature, the coil is capable of quickly translating a corresponding rise in temperature to the solder, to operate the switch 20 and protect the motor 54.

By maintaining the switch 20 at a temperature slightly below the fusing point of the solder, it is possible to eliminate operation of the switch, due to transient overloads of any type that are not harmful to the motor. In other words, the switch 20 will only operate on persistent overload conditions that would cause damage to the motor if allowed to continue.

The motor temperature also aids in maintaining the switch at a given temperature, thus if too heavy a load is impressed on the motor that causes themotor to gradually increase in tem-' perature, the switch 20 will likewise increase in temperature, due to conduction. This maintains the switch at practically the same temperature as the motor, so that operation, free from a time lag, is obtained on overheating of the motor. Thus the switch is sensitive to the temperature of the motor, the temperature 01' the heater, or a combination of the two sources of heat, to act as a protective device, under any type of overload condition.

From the foregoing it will be noted that I have provided a safety cut-out switch to completely protect the motor against injury due to any type of overload or open circuited windings. The resistance coils l1 and .8 may be varied in heating effect to obtain any desired result. For example, only one coil may be used or both coils may be in the circuit continuously. In the latter case, the resistance of the coils should be calculated so that their combined heat output under normal conditions is insufficient to fuse the solder, but that a rise in temperature, in either coil due to overload current, etc., or an abnormally high temperature of the motor will supply the added heat necessary to operate the device.

Another advantage of my construction lies in the series circuit of the coils l1 and 48 with the field windings. This design provides for deenergization of the coils l1 and 48 when the protective device 20 operates to break the circuit. This eliminates burnouts of the heater coils and permits the switch to be reset any number of times in contrast to a fuse type protector which requires replacement after each operation.

My press/it switch provides complete protection for any me I- circuit such as the condenser start, repulsion induction or split-phase types. It prevents burnouts due to an overheated motor, too heavy a load on the motor, open circuited field windings, overload currents, or a stalled motor.

It also provides a manual resetting device so that the switch may be made operative after an emergency 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:

1. In combination with a motor having two phase displaced windings, a circuit breaker in the motor circuit, thermal responsive means for causing opening of the circuit breaker, two heating means in heat transfer relation with said thermal responsive means, one of said heating means being connected in the circuit of one of the windings and the other of the said heating means being connected in the circuit of the other of the said windings, and means for opening one of the winding circuits and deenergizing the heating means therein in response to normal operation of the motor.

2. In combination with a motor having a pair of phase displaced windings, a circuit breaker in the motor circuit, thermal responsive means for causing opening of the circuit breaker, a pair of heating means in heat transfer relation with said thermal responsive means, one of said heating means being energized in response to the flow or current in one of the windings and the other of the heating means being energized in response to the flow of current in the other of the windings, and means for causing deenergization of one of the windings and heating means in response to normal operation of the motor.

3. In combination with a motor having a running winding and a starting winding, a switch in the motor circuit, thermal responsive means for opening the switch when the thermal responsive means is heated to a predetermined temperature, heating means adapted to be energized in response to' energization of the running winding in heat transfer relation to the thermal responsive means, a second heating means in heat transferring relation to the thermal responsive means and adapted to be energized in response to energization of the starting winding, and means responsive to a normal running condition of the motor for deenergizing the starting winding and the last mentioned heating means.

4. In a motor, a power circuit, a pair of motor windings, having circuits connected in parallel in the power circuit, a switch in the power circuit, a temperature responsive means for operating the switch to open the power circuit, a pair of heater elements in heat transferring relation to the temperature responsive means, one of said heater elements being connected in one of the motor winding circuits, and the other of the heater coils being connected in the other of the motor winding circuits, and means for opening 00 one of the motor winding circuits in response to normal running conditions of the motor.

mm C. RANEY.

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