US2311048A - Electric switch - Google Patents

Description

Feb. 16, 1943. M. c. HARROLD 2,311,048

ELECTRIC SWITCH Filed D90. 31, 1940 MGM INVENT R. M%

UNITED STATES i ELECTRIC SWITCH Marshall 0. Harrold, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application December 31, 1940, Serial No. 372,527

-aTENT OFFICE 13 Claim.

This invention relates to refrigeratingapparatus and more particularly to motor controls and electrical controls.

It is an object or my invention to provide an improved and simplified motor control which will adequately control the starting and running of the electric motor and provide automatic protection against overloads.

It is another object of my invention to provide and fastened by the rivet 28 to a pivoted annature 30. The rivet 28 also fastens a bimetal strip 32 to the armature 30.. The pivoted armature 30 is provided with knife edges 34 which are adapted to rock upon the supports 22 with the leaf spring 24 in between. The leaf spring connects the armature 30 to the supports 22 but allows the armature to rock upon the knife edges 34. A set-screw 36 extending through the base an improved and simplified snap-acting mecha- 2D limits the movement of the armature 30 in a nism providing excellent current-carrying propcounter-clockwise direction. I

erties which can be used either with a bimetal The leaf spring 24 extends to an adjusting or another operating means. screw 38 extending upwardly from the base. This It is still another object of my invention to adjusting screw 38 is provided with a spring 40 provide an arrangement wherein a single bimetal and a nut 42 which is prevented from rotating strip may be caused to perform two control funcby a lip which is turned up at the end of the tions. leaf spring hinge. By adjusting the screw 38, the

Further objects and advantages of the present nut 42 is raised or lowered in order to raise or invention will be apparent from the following delower the end of the leai spring 24, which is held scription, reference being had to the accombetween the nut 42 and the spring 40. This panying drawing wherein a preferred form of changes the angularity of the leaf spring 24 and the present invention is clearly shown. thus changes the position of the armature 20 In the drawing: when it is in open position and also changes the Fig. l is a top view of my improved motor opening force of the armature 30, which opposes control; the attraction of its electromagnet 44.

Fig. 2 is a view in elevation 01' my improved The electromagnet 44 is located between the motor control with the overload contacts in closed ppo 21 d the lower 8nd of the armature position and the electromagnetenergized and 30. The left end of the bimetal strip 32 carries with the starting biinetal heated sufilciently to the starting contact 48 which is adapted to make open the starting contacts; contact with a stationary contact mounted upon is a view similar to Fig. 2 in which the an insulated post 48 which is fastened to the overload contacts are in open position and the base 20. The other end of the bimetal strip 32 electromagnet is consequently deenergized; carries the overload contact 50, which is adapted Fig. 4 is a wiring diagram showing the motor to make contact with a stationary contact mountcontrol embodiedin an electric motor circuit in ed upon an insulated post 52 which is fastened one arrangement; to the base 20.

Fig. 5 shows the motor control embodied in an The contact 50 also serves as a rivet for i'aselcctric motor circuit in the arrangement shown tening the bracket 54 to the end of the bimetal. inFigs.1 to 3; and This bracket 54 rigidly holds the two ends 0! a Fig. 6 shows the snap-acting mechanism emspring wire loop 56 which serves as a double bodied in another form of control. toggle type snap-acting mechanism for the right Briefly, I have shown an electric motor startend portion of the bimetal strip 32. This loop ing and overload control including an electro- 56 includes the arms 58 and 80 which have their magnet having a pivoted armature carrying 9. ends extending into opposite sides of the bracket single bimetal strip in which one end serves to 54 to which they are securely fastened. These limit the energization of the starting winding portions 58 and 60 extend substantially parallel and the other end serves as an automatic overto the bimetal strip until they terminate at the load control for the motor. A loop of spring wire sharp bends 62 and 64. From the sharp bends is arranged so as to control the automatic over- 82 and 64 the portions 66 and 68 extend in the load portion of the bimetal strip with a double opposite direction, generally parallel, to the portoggle type snap action. tions 58 and 60 as well as the bimetal strip 32.

Referring to the drawing and more particu- These portions 86 and 68 terminate in a looped larly to Fig. 1 there is shown a motor control portion 10 which is hooked over the adjusting including a base 20, which may be formed of screw 12 with suflicient tension to properly metal or any other suitable material. Extending stretch the bimetal 32 and the loop 58 or spring upwardly from the base are a pair of supports wire. The tension should be such as to cause designated by the reference character 22. Fasthe end of the bimetal strip to snap to open and tened to the sup orts .22 is a l af spring hinge closed positions when heated and cooled as illusconstruction including the leaf spring 24 which trated in Figs. 2 and 3. The spring wire loop is i'astened by the rivets 26 to the supports 22 (i0 56 constitutes a double toggle type snap-acting mechanism without any frictional connections so that it will be more accurate than toggle mechanisms of other types.

In Fig. 5, there is shown diagrammatically an electric motor 14 having a main winding it and a phase winding it. The junction of these two windings is connected to a supply conductor 80 under the control of a suitable control switch 82. The other end oi. the main winding 1% is connected by the conductor 86 to the electromagnet 44 which in turn is connected to the support 22. The phase winding 18 is connected by the conductor 86 to the contact post d8 which in turn connects to the movable contact 46 provided upon the end of the bimetal 32. This end of the blmetal 32 carries the phase winding cur-= rent while the other end carrying the contact 50 carries both the main and the phase winding current. The contact 58 connects to the contact post 52 which in turn may be connected to a heater 54 for applying additional heat to the bimetal 32, if this is found necessary. This heater :3 is connected by the conductor 88 to the supply conductor 96.

In this system, when the switch 82 is closed, current will flow from the conductor 8d through the main winding it, the conductor 84, electromagnet 44 and the right end of the bimetal strip through contacts 50 and 52 and the conductor 88 to the conductor 90. This will cause electromagnet 44 to attract its armature 30 and to cause the contact 46 to engage the contact on top of the insulating post 48. This will cause current to flow through the phase winding E8, the

conductor 86 and the contact 48 as well as the entire length of the bimetal strip 32. This energization will cause the motor 54 to start and pick up speed.

The system is provided with two means for deenergizing the phase winding. It is well known that, as an electric motor picks up speed, the current consumption falls off. This reduces the flow of current through the electromagnet i4 and the opening force provided by the leaf spring 24 will cause the contact 45 to be raised when thecurrent falls off sufliciently. The other opening means is the bimetal 32 itself which will be heated by the flow of the phase winding current through it so that it will curl upwardly and lift the contact it away from the post 33 to deenergize the phase winding. Thus, whichever of these means is first, will control the opening of the phase winding contacts. Under normal voltage conditions the electromagnet 36 will open the contacts prior to the opening by the bimetal 32, but under high voltage conditions the elec= tromagnet 45 does not open the contacts soon enough so that the bimetal 32 takes care of this under those circumstances.

In Fig. 4, the circuit is substantially the same and all parts of the circuit with one exception are given the same reference characters. The difference between the circuit of Fig. 5 and cir cult of Fig. 4 is that, instead of the electromag= net 45 being connected to the support 22,- the electromagnet 44 is connected by a pig-tail connection 94 with the contact 46. With this construction the entire motor current passes through the bimetal 32 from one end to the other. upon the left portion of the bimetal 32 so that this bimetal may be made wider than in the other construction. In all other respects the circults are the same and the circuit and the control operates in the same manner.

This provides a greater heating effect In Fig. 6 I have shown my snap-action mechanism incorporated in an ordinary switch. In this switch, there is provided a supporting means ml which is connected to the source conductor 503. The current-carrying flexible strip of spring metal N35 has one end anchored to the supporting means iti and extends in cantilever fashion therefrom to a bracket iil'i which is ias tened to the end of the strip m5 by the movable contact 509. This movable contact W9 is adapted to make contact with the stationary contact provided upon the top of the insulating post Hi. This stationary contact is connected to the other source conductor l is. My wire loop snap-acting mechanism H5 is connected to the bracket it? as shown in Figs. 1, 2 and 3, and the spring wire is made in the same form shown in these figures. However, in Fig. 6, instead of the wire loop its hooked over the adjusting screw 12 it is looped over the end oi an adjustment lever H9 provided upon the end of a lever arm i ii. The adjustable lever H9 holds the flexible strip Hi5 and the spring wire loop snap-acting mechanism Hi5 a stretched condition. A set-screw i2! is p ovided for adjusting the tension applied to the spring wire loop Hi5. A bellows or any other suitable means may be used to operate the lever Hill to cause the contact N39 to be snapped to open and closed positions just as is shown in Figs. 2 and 3. Thus it will be seen that this simple snap action mechanism may be applied to diilferent types of contact problems.

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

What is claimed is as follows:

1. In combination, a supporting means, :2. flexible strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means having a first portion rigidly connected to said extension and extending therefrom in a dlrection substantially parallel to the strip to a first point adjacent the anchorage of the strip and a second portion extending from said first point to a second point adjacent the rigid connection, and means connected to the spring means for holding the flexible strip in tension.

2. In combination, a supporting means, a flexible strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means having a first portion rigidly connected to said extension and extending therefrom in a direction substantially parallel to the strip to a first point adjacent the anchorage of the strip and a second portion extending from said first point to a second point adjacent the rigid connection, and means connected to the spring means for holding the flexible strip and the spring means in a stretched condition.

3. In combination, a supporting means, a hexible strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means having a first portion rigidly connected to said extension and extending therefrom in a direction substantially parallel to the strip to a first point adjacent the anchorage of the strip and a second portion extending from said first point to a second point adjacent the rigid connection, said flexible strip being provided with means for causing itself to snap to opposite sides of said spring means under the control of said spring means.

i. In combination, a supporting means, a bimetal strip connected to and extending from the supporting means, a double-back type means having a first portion rigidly connected to a point upon said strip and extending from said point generally parallel to the strip to a second point adjacent the connection of the strip with the supporting means and having a second portion extending from said second point to a third point adjacent the rigid connection, a spring means connecting to said second portion adjacent said third point and means connecting to said spring means adjacent said third point, said strip and said first and second portion being displaced to allow the strip to move to opposite sides of the dead-center position.

5. An electrical control including an electromagnet and a movable armature for said electromagnet, a bimetai strip supported upon said armature having its ends extending in opposite directions therefrom, contact mechanisms connected to said strip on opposite sides of said armature, and a snap-acting mechanism for controlling the operation of one of the contact mech anisms independently of the other, said other contact mechanism being operated by the movement of the strip.

6. An electrical control comprising a supporting means, a binietal strip supported at an intermediate point upon said supporting means and having portions extending in opposite directions therefrom, a contact mechanism connected to and operated by each of said portions, and a snapacting mechanism for controlling the operation of one of the contact mechanisms independently of the other.

7. In combination, a supporting means, a fiexible strip anchored at one point to said supporting means and extending in cantilever fashion thereirom to provide a movable extension, spring means having a first portion rigidly connected to said extension and extending therefrom in a direction substantially parallel to the strip to a first point adjacent the anchorage oi the strip and a second portion extending from said first point to a second point adjacent the rigid connection, means connected to the spring means ior holding the flexibis strip in tension, and switch contact means connected to and operated by said movable extenslon.

8. In combination, a supporting means, a flexiblo strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means in the form of spring wire having two portions rigidly connected to said movable extension and extending therefrom in a direction substantially parallei to the strip to points upon opposite sides of the strip adjacent the anchorage of the strip, said spring wire extending substantially in the opposite direction from said points to a third point adjacent the rigid connection, and means connected to the spring means :ior holding the flexible strip in tension.

9. a a flexiblc strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means in the form oi two portions rigidly connected to said movable extension and extending therefrom in a direction substantially parallel to the strip to points upon opposite sides of the strip adjacent the anchorage of the strip, said spring wire extending substantially in the opposite direction from said points to a third point adjacent the rigid connection, means connected to the spring means for holding the flexible strip in tension, and a control device operated by the movement of said movable extension.

10. In combination, a supporting means, a flexible strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, spring means in the form of spring wire having two portions rigidly connected to said movable extension and extending therefrom in a direction substantially parallel to the strip to points upon opposite sides of the strip adjacent the anchorage of the strip, said spring wire extending substantially in the opposite direction from said points to a third point adjacent the rigid connection, means connected to the spring mean:, for holding the flexible strip in tension, and means for providing relative movement between the portion of the spring wire adjacent said third point and the rigid connection.

11. In combination, a supporting means, a flexible strip anchored at one point to said supporting means and extending in cantilever fashion therefrom to provide a movable extension, a unitary member having a first portion rigidly connected to said extension and extending therefrom in a direction substantially parallel to the strip to a first point adjacent the anchorage of the strip and a second portion extending from said first point to a second point adjacent the rigid connection, said strip and said first and second portions being displaced to allow the strip to move to opposite sides of the dead-center position, a portion of said unitary member being resilient, and means connected to said unitary member adjacent said second point for holding said nexible strip in a stretched condition.

12. In combination, a supporting means, a movable member connected at one point to the support and extending in one direction therefrom, a spring wire member having a. first portion connected to said movable member at another point and extending directly from said another point substantially in a straight line to a first pointadjacent said one point and a second portion extending substantially in a straight line directly from said first point to a second point adjacent said another point, and means connected to the spring wire member adjacent said second point for placing the spring wire member and the movable member in tension.

13. in combination, as. supporting means, a flexible strip anchored at one point to said supporting means and extending in cantilever fashion there from to provide a movable extension, 9. spring wire member having a first portion rigidly connected to said extension and extending therefrom in a direction generally parallel to the strip to a first point adjacent the anchorage of the strip and a second portion extending from said first point to a second point adjacent the rigid connection, and means connected to the spring member for holding the flexible strip in tension.

MARSHALL C. HARROLD.

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