US2320942A - Switch - Google Patents

Description

June 1, 1943. E. W. LOGAN 2,320,942

SWITCH Filed Deo, 29, 1939 /A//EA/Toe:

Patented June 1, 1943 UNITED STATES PATENT OFFICE SWITCH Edwin W. Logan, Belleville, Ill., assignor tovThe Emerson Electric Mfg. Co., St. Louis, Mo., a corporation of Missouri Application December 29, 1939, Serial No. 311,538

1 Claim.

lhigh speeds, such as an impulse electric motor,

An object of the present invention is to provide a novel switch of a construction to prevent rebound between the contacts ordinarily caused by the very rapid impact when they come together.

Another object is to provide a novel switch which includes contacts having contact faces so disposed as to deflect contact forces and particularly their reactions that tend to cause rebounding of the contacts. ject is to have contact faces angularly related to the direction of relative movement of the contacts themselves, such that the forces at contact of the surfaces are deflected to have a minimum, if any, component of rebound.

Another object is to provide a novel switch of a construction to provide resilient support for the contacts designed to absorb a part of the forces of engagement between the contacts, and thus dissipate those forces to reduce their effect in producing rebound.

A further object is to provide such a switch having a wiping action between the contacts.

Another object is to provide a switch of simple yet thoroughly efficient construction to obtain the objects and advantages sought therefor.

Other objects and advantages will be apparent from the following description, taken in conjunction with the accompanying drawing, in which Fig. 1 is a view of the present invention in operative combination with a high speed electric motor, the contacts of the switch being shown in contacting relationship, parts being broken away for clarity;

Fig. 2 is a fragmentary view similar to Fig. 1, showing the contacts of the present switch in break relationship;

Fig. 3 is a section on the line 3-3 of Fig. 1;

Fig. 4 is a section on the line 4 4 of Fig. 1; and,

Figs. 5 and 6 are views of modified forms of switches embodying the present invention.

Referring to the drawing more particularly by reference numerals, I0 indicates generally a switch constructed in accordance with the teachings of the present invention disposed in operative combination with an impulse motor generally designated I I.

The impulse motor Il includes a U-shaped iield member I2, on the bight portion of which More specifically, this cbis a winding I4 that, when energized, sets up a magnetic fiu'x producing poles I5fand I6. The

opposite sides of the poles I5 and I6 have cover plates I8, preferably of non-magnetic and electrically non-conducting material, which are secured in place by bolts I9.

A hollow shaft 22 is rotatably supported by bearings in the cover plate, the shaft having a cam 23 secured thereto at a free end disposed exteriorly of one cover plate I8. A rotor 24, of familiar impulse motor shape, is adjustably secured to the shaft 22, by means not shown, to permit adjustment of the cam relative to the rotor.

The switch I0 is operatively mounted on the exterior face of one plate I8. A bracket 21 (Figs. 1 and 4) is secured to the plate I8 by screws 29 A flange 30 of the bracket 21 extends at right angles to the plate I8 and threadedly receives a member 3I having a fiat-faced contact element 32 at one end thereof. A lock nut 28 cooperates with the member 3| to secure the contact element 32 in predetermined position.

The switch I0 also includes a movable member 33 made of spring material comprising an arm 34 secured to the plate I8 by an extension 35 through which screws 36 extend into the plate I3. The arm 34 includes a segment 31 at the free end thereof which is disposed, as by being bent, at an angle (such as 45) to the main portion thereof. A contact element 38 is secured to the segment 31. The main portion of the arm 34 and the segment 31 are in planes at right angles to the plane of the extension 35. A block 40 of insulating material is attached to the arm 34 by screws 4I. The disposition of the arm 34 is such that the block 40 is contacted by the cam 23 to be displaced thereby, after which the arm returns by its resiliency. This movement is approximately at right angles to the direction of movement of the main portion 34 of the switch.

Figs. 5 and 6 show two modifications in which both blades are movable. In Fig. 5 the rst blade 50 has an upturned end 5I and a bent contact element holding segment 52 supporting a contact 53. The second blade 54 is the same as the blade 33, with a main section 55, an end segment least the contacting part of its surface disposed at an acute angle, preferably 45 or more, relative to the direction of relative movement of the contacts. Or, stated diierently, a normal to the contacting surface of at least one Contact is at an acute angle to the direction of relative contact movement.

Operation In the operation of the impulse motor l l there is a rapid make and break action of the contacts 32 and 38 of the switch I0. As is customary in this type of motor, the field winding is in series with the switch, so as to be energized and deenergized twice during a revolution of the rotor,

due allowance being made for any inertia of the" field either in being built up or broken down. Thus, during each revolution of the shaft 22 and hence of the cam 23, there are two complete make and break cycles of the switch l0, inasmuch as the movable arm 34 is moved to the position shown in Fig. 2 twice during one full revolution of the shaft 22. The resiliency of the arm 34 returns it to the position shown in Fig. 1. Manifestly, the number of make and break cycles of the switch I9 is determined by the number of cam surfaces of the cam 30.

Since the motor may operate above ten thousand R. P. M., it is evident that other than a quick, clean, action of the switch is a source of considerable ineliciency. The rapidity of the closing action also causes an exaggeration of the rebound tendency.

As noted, the effective surfaces of the Contact elements 32 and 38, upon which contact is made, f

are at an angle to the direction of movement of the switch arms, which is an angle other than 90, or an acute angle.

Considering the situation wherein the contact element 32 is xed and theelernent 38 moves against it, the angle between the contacting surfaces is such that the moving Contact, upon striking the xed one, is given a delecting tendency with its angle of reflection approximately equal or related to the angle of incidence. For this reason, if the angle between the surfaces is as much as 45 to the direction of movement of the contact, the deilection force has Vno component in a direction to cause rebound. A lesser angle is vadvantageous over a flat switch blade, buty the larger angle increases the advantage, and the angle at which there is no component of rebound is best.

In addition, the fact that the forces of contact and rebound may act against the bent-over switch blade ends, enables the switch blade to absorb some of the force of contact in a ready deflection of these ends. Preferably both ends are bent, and the bending is such that the righting force component is not in the direction of rebound. In Fig. 2, the force is partially absorbed in bending of the segment 3l about its union with the portion 34.

This bending may also be transmitted through to other parts of this resilient member.

The deflection of the bent end also provides a wiping action of the contacts, since it shortens the length of the resilient switch arm 33 to enable the arm to move further toward the rotor axis. In so doing, the contact elements are necessarily together and one wipes across the other.

The modifications of Figs. 5 and 6 work on the same principles, since the movement of both arms may be resolved into movement of one relative to the other, assuming the second to be relatively iixed. These types have the advantage that both blades are resilient to absorb the Contact impact.

It is understood that the foregoing description and accompanying drawing have been given by way of illustration and example and not for purposes of limitation, the invention being limite only by the claim which follows.

What is claimed is:

A switch comprising a relatively xed iirst contact element, a movable switch arm, a second contact element thereon, means adapted to operate said switch arm so that the contact element thereon moves to and away from the rst contact element, said means and said contact elements being arranged so that for a substantial part of the interval of time during which the contact elements are in contact with one another, the surface along which the Contact elementsv touch each other makes an acute angle of substantially element on the switch arm.

EDWIN Vif. LOGAN.V

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