US1994308A - Mechanism for magnetic motor starters - Google Patents

Description

March 12, 1935. w, GQFF 1,994,308

MECHANISM FOR MAGNETIC MOTOR STARTERS Filed Nov. 23, 1932 Robert W GoFfi His Abisorheg.

Patented Mar. 12, 1935 UNITED l STATES PATENT OFFICE MECI IANISM FOR MAGNETIC MOTOR STARTERS Robert W. Goff, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 23, 1932, Serial No. 644,048

9 Claims.

mechanism therefor.

While it is not limited thereto, my invention is particularly applicable to motor starters of the magnetically operated type. Heretofore in the design of motor starters much has been left to be desired in securing a constant torque on the timing device and a constant pressure of a predetermined value on the contacts of the starter. Furthermore considerable wear of the gears connecting the timing device to the solenoid has been caused by the sliding of a rack gear over a timing gear during the opening of the starter.

In carrying out my invention in one form thereof I provide a spirally wound spring which is normally maintained under a predetermined tension with means for applying the potential force of the spring to operate the switch contacts and the timing mechanism. More specifically I provide an operating shaft for operating the accelerating contacts, with one end of a spiral spring attached to an enclosing casing which casing is secured to the shaft. The other end of the spring is secured to a member having an arcuate slot cooperating with a projection provided on the casing. The energy of the spring is applied to the shaft by rotating the member so that its slot frees the projection and thereby applies the torque of the spring to the operating shaft. The speed of rotation of the operating shaft during the closing of the contacts is controlled by a timing device, which device is positively connected to the driving shaft at all times.

For a more complete understanding of my invention reference should now be had to the drawing in which Fig. 1 illustrates a front elevation of a magnetic starter embodying our invention; Fig. 2 is a side elevation of Fig. 1; Fig. 3 is a sectional elevation taken on the lines 3--3 of Fig. 1; Fig. 4 is a sectional elevation taken on the lines 4-4 of Fig. 2; Fig. 5 illustrates an exploded view of the spring motor employed to operate the timing mechanism, while Fig. 6 shows in perspective the manner of locking the timing gear to the driving gear during the closing of the switch contacts.

Referring to the drawing I have shown my invention in one form as applied to the operation of a magnetic starter 10 provided with a plurality of contacts 11 to 15 inclusive which under the joint control of a solenoid 18 and a timing device 19 control the motor or load circuit.

The timing device per se forms no part of the present invention. It is fully disclosed and broadly claimed in the copending application Serial No. 644,049, filed November 23, 1932, Goff et al., and assigned to the same assignee as the present invention. Other types of timing devices may be utilized, for example, a device of the type described in French Patent 636,342.

Continuing the description of my invention, the plunger 20 of the solenoid is connected to one end of a lever 21 by means of a pin 22. The

other end of the lever 21 forms a part of the contact operating member 23. The accelerating contacts 13, 14 and 15 are arranged to be closed in time sequence, each contact arm being secured to the end 25 of the shaft 26; which shaft also forms a support for the member 23. The only connection between the member 23 and the shaft 26 however is provided by a spirally wound coil spring 28. As shown in Fig. 5, the inner end of the spring is connected to a hub portion 29 of a flange 30 provided on the member 23, by means of a slot 31. The outer end of the spring extends through a slot 33 of the enclosing casing 34, the hub of which is secured to the shaft 26 by a pin 35. The coil spring 28 is normally main.- tained under tension so that the normal tension of the spring can be applied to the shaft 26 to close the contacts 13 to 15, inclusive. The normal tension of the spring is obtained when the switch is assembled. For example, the inner end of the spring is placed in the slot 31 and the outer end of the spring is placed in the slot 33. The enclosing casing 34 is then rotated in a counterclockwise direction until an extension 36 from the casing coincides with an arcuate slot 37 provided by the flange 30. It will now be observed that the normal tension of the spring is applied to the shaft 26 whenever the solenoid 18 rotates the member 23 and the flange in a clockwise direction. The function of the arcuate slot 37 is to clear the path for the projection 36. By maintaining the coil spring under tension and applying the resultant force to the shaft 26 a substantially constant rotative effort is maintained throughout the closing of the contacts 13 to 15, inclusive. Furthermore this same effort of substantially constant magnitude is effective in maintaining the contacts 13 to 15 in their closed positions.

The timing device 19 controls the time of operation of the switches 13, 14 and 15. The device 19 is connected to the shaft 26 by means of a gear segment 40 arranged to mesh with a timer driving gear 41. Referring to Figs. 3- and 4, it will be seen that the gear 41 is secured to a shaft 42 supported in a bracket 43 formed from the enclosing casing 44 of the timing device. The timing device itself is operated by a ratchet gear 45 connected to the shaft 42 by means of a oneway clutch 46. An escapement 48 and an oscillating weight 49 are connected together by means of a member 50 secured to the escapement as by the screws 52. The member 50 and the oscillating weight 49 are respectively provided with slots 54 and 55 so that a bodily movable adjusting screw 56 may be secured in any position along the lengths of the slots. It will be observed that the oscillating weight 49 is pivotally supported at its center to the shaft 42 by means of a bushing 58. By loosening the adjusting screw the are through which the oscillating weight is moved under the influence of the escapement 48 may be varied from zero to a maximum. As shown, a ratio of 10 to 1 may be secured for the timing device; that is to say, the time of closing of the contacts :13 to 15 may be varied from one second to ten seconds. The minimum time is secured by moving the adjusting pin 56 until it is in coaxial relation with the pivot 59 of the escapement 48. By increasing the length of the oscillating weight between the shaft 42 and the pivot pin 59 of the escapement 48 the range of operation may be greatly increased.

In the operation of my invention it will be assumed that the parts are in the positions shown in the drawing. As soon as the solenoid 18 is energized the plunger 20 operates the member 23 (Fig. 5) in a clockwise direction so as to clear the path for the projection 36 on the enclosing casting 34. At the same time the member 23 closes the line contacts 12. In addition to clearing the path for the extension 36 the rotation of the member 23 by means of its hub portion 29 winds the coil spring 28 so as to increase the rotative effort applied by the spring 28 to the shaft 26. As the shaft 26 begins to move, the driving gear 41 rotates the inner member 61 of the one-way clutch so that the ball bearing 62 biased by a spring 63 forms a driving engagement with the inner surface of the ratchet gear 45 and the member 61 of the clutch. As a result of the driving effort on the ratchet gear 45 the escapement 48 is oscillated about its pivot 59. For each oscillation of the escapement, the oscillating weight must be moved through an arc sufficient for the escapement to disengage itself from a tooth of the gear 45. The oscillating weight is then driven back and forth and provides a positively operated time delay for the operation of the contacts 13 to 15.

Inasmuch as the closing of the last accelerating contact 15 applies full line voltage .to the motor (not shown) provision is made for the quick closing of this contact by the omission of the gear teeth at .the end 65 of the gear segment 40. Consequently as soon as the timing gear 41 leaves the gear teeth on the segment 40, the spring 28 accelerates the movement of the contact 15 to its closed position. However, the gear 41 is maintained in a fixed position so that its gear teeth will move into exact meshing relationship with the gear segment 40 upon the deenergization of the solenoid 24. This is accomplished by providing a locking projection .67 on the gear segment 40. The projection axially extends a short distance beyond the plane of the segment and opposite the end 65 of the segment gear 40. Co-

operating with the projection 67 is a locking projection 68 provided on the gear 41. The locking projection 67 at its outer surface '10 is curved, the radius of the curve being the same as for the gear teeth of the segment. The locking projection 88 is provided with a depression 71 which is arranged to engage the curved surface '10 as the gear teeth become disengaged. Thus while the contact 15 is released from the action of the timing device 19, the cooperating locking projections fix the position of the gear 41 with respect to the gear segment 40 as shown in Fig. 6.

After the accelerating contacts 13, 14 and 15 have been closed, a projection 340 formed on the casing 34 opens the contacts 11 to reduce the energization of the motor ileld winding (not shown).

If at any time the solenoid 18 is deenergized the weight of the plunger and of the switch mechanism is sufllcient to return the parts to the positions shown in Figs. 1 and 2. As soon as the return movement begins, the ball bearing 62 disengages itself from the clutch member 61 and the ratchet gear 45 so that the timing device does not interfere with the opening of the contacts. The locking projection 68 slides along the curved surface '10 of the projection 6'7 until the teeth of gear 41 engage the teeth of the segment gear 40. Due to the fixing of the position of the gear by the locking projection, the teeth always come into exact meshing relationship with each other. Consequently the wear on the teeth is reduced to a minimum and the sliding of one gear over the other has been entirely eliminated.

In order to adjust the rate of closing of the contacts 13 to 15 to accommodate the motor starter to various sizes of motors, it is only necessary to loosen the nut of the adjusting screw 56 and to move the screw towards the shaft 42 to increase the time of closing or to move the screw 56 towards the escapement 48 to decrease the time of closing. If, for example, the adjusting pin or screw 56 is secured with its axis coinciding with the axis of the pin 59 of the escapement, the oscillating weight 49 will remain stationary and the contacts 13 to 15 will close at substantially the same time as the line contacts 11. The result of moving the adjusting screw 56 towards the shaft 42 is to increase the mass which must be moved by the escapement 48 for the progression of the ratchet gear 45 and it is in this manner that the exceedingly wide range of operation is secured.

While I have shown a. particular embodiment of my invention, it will be imderstood of course that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a motor starter having a plurality of contacts, a shaft for operating said contacts, a solenoid, and a driving connection between said solenoid and said shaft comprising a spirally wound spring normally under tension having one end connected to said shaft and the other end operatively connected to said solenoid.

2. In combination, a plurality of contacts, a shaft for operating said contacts, a solenoid, a driving connection between said solenoid and said shaft comprising a spirally wound spring having its inner end operatively connected to said solenoid and its outer end connected to said shaft, and means for maintaining said spring under a path of said extension so as to apply the tension predetermined tension, said means being arranged to apply said tension to said shaft whenever said solenoid is operated.

3. In combination, a plurality of circuit controlling contacts, a shaft for operating said contacts, a solenoid, a driving connection between said shaft and said solenoid comprising a spirally wound spring, connections for connecting one end of said spring to said solenoid and the other end to said shaft, the said connection normally maintaining said spring under a predetermined tension, means for energizing said solenoid to increase the tension of said spring and to apply all of its tension to rotate said operating shaft, and timing means for controlling the speed of said shaft. 1

4. In combination, a plurality of circuit controlling contacts, a shaft for operating said contacts between'open and closed circuit positions, a solenoid movable between predetermined positions, a driving connection between said solenoid and said shaft comprising a spirally wound spring,

a member arranged to be rotated by movement of said solenoid, fastening means for securing the inner end of said spring to said member, a driving member for said shaft, means for securing the outer end of said spring to saiddriving member, a projection on said driving member arranged to cooperate with a slot provided in said first mentioned member to maintain said spring under a predetermined tension, and means for energizing said solenoid to rotate said first mentioned member so as to free the path of said projection and to apply the tension of said spring to close said contacts and to bias said contacts in their closed position by said predetermined tension.

5. In combination with a switch, an operating shaft therefor, a plurality of contacts arranged to be closed in succession by said shaft, a timing device for retarding the closing of said contacts, additional contacts on said switch, an operating member for said additional contacts for closing said additional contacts independently of said plurality of contacts, a solenoid directly connected to said operating member and operable from one position to another, a coil spring normally under tension connected respectively. to

said member and to said operating shaft, and

means for, applying the tension of said'coil spring to said operating shaft whenever said solenoid is operated from said one position to said other position.

6. In combination, a plurality of circuit controlling contacts, a shaft for operating said contacts from open positions to closed positions a solenoid operable between predetermined posh tions, a driving connection between said shaft and said solenoid comprising a spirally wound spring,

whenever said solenoid is operated to free the p of said spring to said shaft.

7. In combination, a shaft arranged for rotation from one to another position, a plurality of a normally open contacts arranged to be closed in succession by rotation of said shaft, a solenoid, means for maintaining a predetermined contact pressure when said contacts are closed comprising a spirally wound spring, means for maintaining said spring under a predetermined tension and for applying said spring tension to rotate said shaft whenever said solenoid is operated, and a timing device for delaying the speed of rotation of said shaft, the character of said spiral spring being such that a substantially constant effort is applied by said spring to turn said shaft from one to the other of said positions and to hold said contacts closed.

8. In combination, a circuit controller having a pluralityof contacts, an operating shaft movable from one position to another for successively closing said contacts, a solenoid, a driving connection between said solenoid and shaft comprising a spiral spring, connections for connecting one end of said spring to said solenoid and the other end of said spring to said shaft, the said connections normally maintaining said spring under a predetermined tension, means for operating said solenoid to. apply the tension of said spring to rotate said shaft, a timing device for delaying the speed of rotation of said shaft, a driving gear having a predetermined number of teeth secured to said shaft, a timer operating gear arranged to be engaged by said gear teeth during a portion of the movement of said shaft, and locking means on said gears for holding said timer operating gear in a predetermined position during the remainder of the movement of said shaft.

- 9. In combination, a circuit controller having a plurality of contacts, an operating shaft movable from one position to another for successive- 1y closing said contacts, a solenoid, a member operated by said solenoid, a driving connection between said solenoid and shaft comprising a spiral spring, connections for connecting one end of said spring to a member operated by said solenoid and the other end of said spring to said shaft, the said connections normally maintaining said spring under a predetermined tension, means for operating said solenoid to apply the tension of said spring to rotate said shaft, a timing device for delaying the speed of rotation of said shaft, a driving gear for operating said device, a one-way clutch connected between said gear and said device for operating said device for one direction of rotation of said gear, a driving shaft, a gear segment secured to said shaft and provided with a plurality of gear teeth operable into and out of meshing engagement with the teeth on said gear, a locking projection on said gear segment extending. beyond the ends of said gear teeth, a locking member provided with a depression axially extending from said gear for engaging said locking projection when said element is moved to disengage said teeth thereby to hold said gear in a predetermined position.

ROBERT W. GOI'I'.

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