US2801312A - Electrical apparatus - Google Patents

Description

July 1957 H. F. CLARK ELECTRICAL APPARATUS Filed June 12, 1953 INVENTOR. Harry E Clark His Aflomey Hg a United States Patent ELECTRICAL APPARATUS Harry F. Clark, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 12, 1953, Serial No. 361,198

2 Claims. (Cl. 200-87) This invention relates to electrical apparatus and more particularly to an improved starting system for high starting torque split phase motors.

Single phase induction motors are provided with a phase winding for starting. A starting control is provided for insuring the full energization of such a winding during the starting period of the motor and a deenergization or reduced energization of such a winding during the running period. The operation of the starting control at the proper time as well as the design of the motor determines the maximum starting torque which can be exerted.

It is an object of my invention to provide an inexpensive starting control which will insure the most satisfactory energization of the phase winding over as wide a voltage variation in single phase power supply as may be found throughout the United States.

It is another object of my invention to provide an inexpensive starting control which will close instantaneously upon connection of the motor to the supply source and which will deenergize or change the energization of the phase winding when the proper speed is reached under a wide variation in voltage supply such as 90 to 125 volts.

It is. another object of my invention to provide an inexpensive starting control which is easily set for operation within acceptable limits;

It is another object of my invention to provide an inexpensive multiple purpose electromagnetic starting control with a main electromagnet coil and an opposing or bucking electromagnet coil in which the relationship and the number of turns of each are proportioned to cause the control to operate at the proper time with various sizes of small motors whether or not they are provided with a capacitor over a wide variation in supply voltage such as 90 to 125 volts.

These objects are attained by winding as a single unit the main electromagnet coil and the opposed or bucking electromagnet coil upon a fiat bar which is offset at one end of the coils and bent in the same direction at the other end. of the coils. This flat bar is staked edgewise at two parts to a flat base of insulating material. The offset portion serves as the spring support for the flat bar armature which carries a lead weight and a felt cushion to minimize chattering. The base carries a stationary contact.

The base also has staked edgewise to it a second L-shapedfiat bar member which carries the operating bimetal and the compensating bimetal of a snap acting overload switch mechanism which is connected to one side of the supply source. This second bar carries the anchored end of a. leaf springcontact mechanism carrying'a contact adapted to make and break engagement with a'st ationary contact. This leaf spring has a projection extending into contact with the armature when the armature is in the open circuit position and it is sprung so that it will engage the stationary contact when the armature is pulled away from it by deenergization of the main.

electromagnetcoil. The main electromagnet coil is con- 2,80 1,3 12 Patented July 30, 1

nected in series with the main winding while the opposed or bucking coil is short-circuited or connectedin series with the phase winding which is also connected in series with the stationary contact and the leaf spring actuated contact.

Further objects and advantages of the present inven tion will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.

In the drawing:

Figure 1 is a plan view of one form of a starting control embodying my invention together with a diagram of the motor circuit;

Figure 2 is a sectional view taken along the line 22 of Figure l; i

Figure 3 is a sectional view taken along the line 33 of Figure 1;

Figure 4 is a bottom view of the control shown in Figure 1; and

Figure 5 is a wiring diagram of a modified form of control in which the opposing or bucking winding is connected in series with the phase winding.

Referring now to the drawing and more particularly to Figure 1 there is shown a flat base 20 of electrical insulating material such as a phenolformaldehyde resin. Staked edgewise to this base by the projections 22 and 24 extending through slots in the base 20 is a pole piece 26 having an offset portion 28. Between this oifset portion 28 and the opposite end is a main electromagnet coil 30 which is wrapped around the wide fiat bar material of soft iron which forms the pole piece 26. This main electromagnet coil preferably is made of Number 20 or Number 22 insulated wire and has about 35 turns of Number 20 wire wrapped around the pole piece 26.

To secure better operating characteristics when the control is applied to motors of dilferent sizes and subjected to wide voltage variations I also provide an opposing or bucking winding 32 of approximately 15 turns of Number 20 wire which is preferably short-circuited by ice having both of its ends connected to the pole piece 26 These windings 30 and 32 are'distributed uniformly along the portion of the pole piece 26 located between the two bent portions. However, with less satisfactory results this opposing winding 32 may be connected in series with the phase winding as in Figure 5 or even in series with the common or supply line. More turns may be provided in the main coil 30 but this must be counteracted by providing the armature with a higher rate return spring.

The offset portion 28 is provided with a bent end por-' tion 34 to which is attached one end of a thin leaf return spring 36. The thin leaf spring 36 is substantially straight so that no bending is required of it since the proper angularity is assured by the bent portion 34. Connected to the free end of the leaf spring 36 is a flat bar armature 38 of soft iron or other magnetic material. This extends in substantially the same direction as the pole piece 26 and at its free end preferably carries on its opposite faces pads of lead 40 having a combined weight of about A of an ounce. The free end of the armature 38 is adjacent the one end of the main coil 30. The magnetic circuit is completed by bending transversely the one end 42 just beyond the free end of the armature 38 in the same direction as the offset and the armature 38. This assures that there will be no pronounced click or noise when the armature 40 is attracted. The energization' of the main coil 30 attracts the armature 40 toward the coil 30 and this movement toward the coil 30 is cushioned by a felt pad 44 provided on the adjacent surface of the lead pad 40.

the base 20 which are staked beneath the base to hold the bar firmly in place. This bar 46 has spot-welded to it the anchor end of a Z-shaped leaf spring 52 carrying a movable contact 54. This movable contact 54 is adapted by the spring force inherent in the leaf spring 52 to make engagement with the upper portion of an L-shaped stationary contact 56 having its base portion beneath the base 20 and riveted to it. The upper transverse portion 58 of the leaf spring 52 extends into engagement with the armature 38 when the magnet coil 30 is deenergized as shown in Figure 1 so that the contact 54 is held away from the stationary contact 56. When the armature 38 is attracted it will pull away from the leaf spring 52 to allow the spring force in the leaf spring 52 to carry the movable contact 54 into engagement with the stationary contact 56. The attraction of the electromagnet coil 30 causes the substantial closing of the magnetic circuit to hold the armature so that the pad 44 is pressed tightly against the coil 30 which acts also as a stop member. In the attracted position, the armature 38 is away from the adjacent end 58 of the leaf spring 52 so that any vibration or chattering of the armature will not affect the engagement of the contacts 54 and 56 during the starting period when they are closed so that there will be no intermittent arcing.

The reversed L-shaped bar member 46 also has fastened to it the base of a reversed L-shaped overload bimetal strip 60carrying at its free end a movable contact 62 adapted to make engagement with the upper portion of an L-shaped stationary contact 64 having its base portion located beneath the base 20 and riveted to it. The bar member 46 also has fastened to it the straight portion of a hooked shaped overload compensating bimetal 66. Extending through an aperture in the free end of the bimetal strip 60 and a notch or aperture in the end portion of the overload bimetal 66 is a multiple leaf reversed C-shaped spring member 68 which provides a double throw toggle action to cause the contact 62 and the bimetal strip 60 to move when heated with a snap action away from the stationary contact 64. This opening movement is stopped by an edgewise mounted bar type stop member 70 having a projection 72 extending through a slotin the base 46 and staked to fasten the member 70 in place. The member 70 at the end opposite the bimetal strip 60 extends to form a stop for limiting the opening movement of the armature 38 as shown in Figure 1.

The supply conductor 74 is connected through a control switch 76 with the L-shaped contact member 64. Current flows through the contact 64 and the bimetal strip 60 to the bar member 46 through which it is conducted to a connecting strip 78 which connects to the pole piece 26. This current is then conducted through the pole piece26 to the one end of the main electromagnet coil 30 and thence flows through this coil to the other end which is connected preferably beneath the base 20 by a conductor 80 connecting to the main winding terminal 82 also located beneath the base 20. This main winding terminal 82 is connected by a conductor 84 beneath the base 20 to the main winding 86 of the motor 88.

The stationary contact 56 is connected by a conductor 90 beneath the base 20 to one end of the phase winding 92 of the motor 88. The adjacent ends of the main and phase windings 86 and 92 are connected to the other supply conductor 94.

The current required to trip the overload bimetal strip 60 to the open circuit position is controlled by bending the stationary contact 64. The reclosing of this control is controlled by the adjustment of the setscrew 96 which extends through the bar members 46 into contact with the base portion of the overload bimetal strip 60. To prevent the unintentional turning of this screw 96 under various conditions of vibration there is provided a friction spring 98 shaped as illustrated in Figure 4 which extends between the setscrew 96 and the base 20. The armature 38 may be adjusted. or set to vary the operation of the 4 contact 54 by bending the bent end 34 to the position giving the best results.

The opposing or bucking coil improves the performance of the relay. It makes possible a lower current differential between the pull in or closing of the relay and the drop out or opening of the relay. The lower differential makes possible the closing of the relay upon a lower supply line voltage while without any change in calibration it permits the dropping out or opening at a higher supply voltage. This makes it possible for this starting control to operate better than a single coil relay of similar design over a wider range of voltages such as to volts for various sizes of split phase motors such as from H. P. to H. P. regardless of whether or not a capacitor is used for the phase winding circuit.

In Figure 5 there is shown a modified form of the invention in which there is used a similar pole piece 126 having an offset portion 128 to which is fastened a leaf spring 136 which connects to a flat armature 138. The armature 134 is provided at its free end with a shortcircuiting copper ring 139. This short-circuited copper ring is also used to fasten to the armature 138 a contact arm 152 carrying a movable contact 154 which is adapted to make engagement with the stationary contact 156 when the armature 138 is attracted. In the open circuit position the short-circuited copper ring rests against a stop 170.

The pole piece 126 is provided with a main electromagnet coil and an opposing or bucking electromagnet coil 132. The junction of these two coils is connected by the conductor 173 to a control switch 176 which controls the flow of current from the supply conductor 174. The contact 156 is connected by the conductor 190 to the one end of the phase winding 192. The one end of the opposing or bucking coil 132 is connected by the conductor 133 to the leaf spring 136 which conducts the current to the armature 108 through which the current is conducted to the starting contact 154. The other end of the main winding is connected by the conductor to one end of the main winding 192 of the motor 188. The common junction of the main and phase windings is connected to the supply conductor 194. The phase winding circuit may be provided with a capacitor 191 which may be omitted if desired when an ample starting torque is obtained without its use.

This starting control may be operated with the face up or face down as shown or with either of the notched edges up or down. In general however, it will not be satisfactory to mount the control with either of the smooth or side edges up or down. I find that this control is easy and inexpensive to manufacture and satisfactory and durable.

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 as may come within the scope of the claims which follow.

What is claimed is as follows:

1. An electromagnet including a base of electrical insulating material, a wide fiat bar positioned edgewise upon and fastened to said base, said bar being of magnetic material and being offset in one direction at an intermediate point, a leaf spring positioned edgewise relative to said base connected to said offset portion and extending to- Ward the other end, an armature in the form of a flat wide bar of magnetic material positioned edgewise relative to said base and connected to said leaf spring, said leaf spring being biased to move said armature away from said first mentioned bar, the adjacent end of said first mentioned bar being bent toward and beyond the free end of said armature, an electromagnet coil wrapped around said .first mentioned bar between the offset and the bent end, an electrical contact supported by said base, a second leaf spring positioned edgewise relative to said base and having a portion anchored to said base, said second leaf springhaving a movable portion carrying a contact and being biased opposite to said leaf spring toward said armature and said bar to move its contact into engagement with said contact supported by said base, said second leaf spring having a projection disconnected from but extending into the path of movement of and contacted by said armature in its movement away from said first mentioned bar to separate said contacts.

2. An electromagnet including a wide flat bar of magnetic material offset in one direction at an intermediate point, a first spring having one end connected to said offset portion and extending toward the other end, an armature in the form of a wide flat bar of magnetic material connected to the other end of said first spring and extending in substantially the same direction as the free end of the first spring, the end of said first mentioned bar being bent toward and beyond the free end of said armature, said first spring being biased to move said armature away from said first mentioned bar, an electromagnet coil wrapped around said first mentioned bar between the offset and the bent end, a normally stationary contact, a second spring member carrying a movable contact portion biased opposite to said first spring toward said armature and said bar for engagement with said stationary contact, said second spring member being provided with a projection located in the path of movement of said armature away from said bar.

References Cited in the file of this patent UNITED STATES PATENTS 316,707 Weston Apr. 28, 1885 863,667 Struble Aug. 20, 1907 1,961,058 Mace May 29, 1934 1,981,259 Wertz Nov. 20, 1934 2,021,199 Pearce Nov. 19, 1935 2,076,849 Kennedy Apr. 13, 1.937 2,290,489 Nelsen et a1. July 21, 1942 2,477,120 Ecker July 26, 1949 2,491,643 Burks Dec. 20, 1949 FOREIGN PATENTS 76,559 Austria May 26, 1919 100,732 Great Britain Aug. 17, 1916 531,282 Germany Apr. 5, 1930 845,757 France May 22, 1939

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