US2505548A - Electric switching device - Google Patents

Description

April 25, 1950 P. HUTT 2,505,548

ELECTRIC SWITCHING DEVICE Filed May 17, 1949 Inventor: philip Hutt His Attorneg.

Patented Apr. 25, 1950 ELECTRIC SWITCHING DEVICE Philip Hutt, Milford, Conn., assignor to General Electric Company, a corporation of New York Application May 17, 1949, Serial No. 93,736

This invention relates to an electric switch of the rotary type, and more particularly to such a switch in which movement of the switch blade over fixed contact positions takes place with a snap action.

It is a primary object of my invention to provide an electric switch having a rotary switch blade sweeping over a plurality of contact positions in which movement from one contact position to an adjacent position takes place with a snap action.

More particularly, it is an object of my invention to provide an improved switch construction having a positive stepping action of the movable contact arm or switch blade as it moves from one contact position to an adjacent contact position in either direction.

A further object of my invention is to provide an improved multi-position switch capable of quickly making or breaking an electrical circuit as a control knob is operated in order to avoid arcing between the contacts and delays in the switching operation.

More specifically, my invention is directed to an improved switch construction particularly adapted for multiple speed electric fans requiring a switch with an off position and a plurality of steps in the on position for regulation of fan speed.

In accomplishment of the foregoing objectives, a feature of my invention consists in arranging a movable switch blade on an insulated base so that the switch blade may sweep over a plurality of contact positions with a stepping motion, the driving engagement between the operating handle and the movable switch blade being arranged to permit a limited movement of the operating knob with respect to the switch blade, and after such movement, to suddenly increase the torque applied to rotate the switch blade without application of additional force.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a side elevation of this switch mounted in a horizontal position; Fig. 2 is a front elevation of the mounted switch; Fig. 3 is an end view illustrating in detail the base of the switch; Fig. 4 is a cross-sectional view taken on the line 44 of Fig. 1; Fig. 5 is a cross-sectional view taken on the line 55 of Fig. 1; Fig. 6 is a cross-sectional view taken on the line -6 of Fig. 1; Fig. '7 is a cross-sectiona1 view taken on the line 8-8 of Fig. 1 in a differ- 5 Claims. (Cl. ZOO-65) ent operative position from the position shown by Fig. 6; and Fig. 8 is a cross-sectional view taken on the line 8-8 of Fig. 3.

Referring to the drawing, a switch assembly is shown for a multi-speed electric fan. It is to be understood, however, that this invention is not limited solely to this particular application, this switch being equally suitable for other applications where a snap action switch is required. The switch is mounted on any suitable wall portion i, such as a fan base, and for this purpose a nut 2 and serrated ring 3 are threaded Onto a barrel 4 with the nut on one side of the wall I and the ring on the opposite side. The switch assembly may thus be mounted in an appropriate position extending through an aperture provided in wall I. A knob 5 provides a means for manually operating the switch to either an off position or a plurality of on positions, as shown by Fig. 2, corresponding, for example, to a plurality of speeds for a fan. Barrel 4 carries on its end opposite handle 5 a bracket member 6. Bracket member 6 provides the means for supporting insulating base 1 in a fixed position. A central terminal 8, mounted on base '1, provides a connection through a switch blade 9 to any one of the outer terminals II), II, and I2.

The base I, of insulating material, is the supporting member for the movable switch blade 9 and the fixed contacts made up from the terminals H), II. and I2. One end of base I has a plurality of notches l3 for receiving terminals 10, ll, and I2. As best shown by Fig. 8, terminal l2 extends outwardly from the back side of base i. A portion of terminal I2 is bent over to lie in contact with the inside face of base l2 to form the fixed contact it. The end l5 of terminal i2 is bent over and forced through an aperture [6 in base 1 to anchor terminal ii in position. Likewise, terminals l0 and H are mounted on base I to form the fixed contacts I! and i8 as best shown by Figs. 6 and 7. In this particular embodiment, a terminal and contact element are not provided for the notch IS in the base so that there will be an off position for the switch. As shown by Fig. 3, base i is provided with a pair of apertures 20 and 2| for attachment of the base to bracket 6 as will appear later. Along the end of base i diametrically opposite from terminals H), H, and I2 and off position iii, are apertures 22, 23, 24, and 25, respectively. These apertures cooperate with switch blade 9 to restrain its rotary movement to aid in achieving a step-by-step movement of switch bladeil.

Frame 6, for supporting base I in spaced rela- 3 tion from barrel 4. is in the form of a U-shaped metal bracket. Each of the legs of frame 3 has an end portion of reduced width for projection through apertures 23 and 2| in base 1. With base 1 in position, these end portions 23 and 21 are peened over to secure frame 3 and base I in assembled relation, as shown by Fig. 4. For attachment of frame 3 to barrel 4, the connecting portion 23 of frame 3 is centrally apertured at 23, as shown by Figs. 4 and 5. At diametrically opposite points in aperture 23, projections 33 and 3| extend inwardly from the other wise circular aperture 23. It is these projecting portions 33 and 31- which serve as stops to limit the rotation of knob 3. Barrel 4, which is cylindrical in shape, has an end portion projecting through aperture 23 in frame 3, and this end portion is rolled over, as at 32 to anchor the barrel to the frame. This end portion of barrel 4 is slotted so that the barrel, in projecting through the central aperture 23, may fit around the projections 30 and 3|. Frame 3 and barrel 4 are thus secured together in a manner preventing any relative displacement.

Barrel 4 serves two primary functions. It is cylindrical in shape and is threaded on an outer surface for engagement with clamping nut 2 and ring 3 in order to support the switch assembly on wall member I. The inner cylindrical surface of the barrel provides a bearing surface for the rotataole shaft 33 which is connected to knob 5.

The form of the rotatable switch blade 3, best shown by Figs. 6, 7, and 8, is adapted to establish electrical connection between the center terminal 3 and one of the outside terminals I3, I I, or l2. Switch blade 3, fabricated from resilient electrical conducting material, has an end portion 34 with flared-out edges to facilitate its movement across the contacts l4, l1, and i3. Switch blade 3 is attached to base 1 so that it may rotate with respect to base 1 and sweep over the fixed contacts. The opposite end of switch blade 3 is provided with a dimple 35 receivable in one Of the apertures 22, 23, 24, or 23 in base 1. The cooperation between dimple 35 and the apertures in the base tends to restrain movement of switch blade 3 and to maintain the switch blade in one of the contact positions. In this connection, it will be noted that the apertures 22 through 23 are diametrically opposite from the four contact positions.

Switch blade 3 is driven in its rotation in either direction by means of a spring clip 33. Clip 33 is formed from a generally U-shaped strip of resilient material with its outer end portions 31 and 33 bent inwardly for engagement with a portion of shaft 33, as shown by Fig. 4. Switch blade 3 and clip 33 are mounted on base I by means of a rivet 33, which additionally serves as a means for amxing central terminal 3 to base 1.

The position of switch blade 3 is manually controlled by knob 3 carrying a shaft 33. Shaft 33 has a portion of cylindrical shape adjacent knob 3, rotatably received within barrel 4. The remainder of shaft 33 is flat for driving engagement with spring clip 33. The outer extremity 40 of this flat portion of the shaft is flared outwardly and provided with bevels leading to the tip to form a small knob. This construction facilitates assembly since it is merely necessary to insert the shaft within barrel 4 and by pressing inwardly on handle 3, the extremity 43 of the shaft is forced between the legs of clip 33, and the flared portion prevents accidental withdrawal. As best shown by Figs. 4, 6, and 7, each flat side of shaft 33 is provided with a bevel extending to the outer edge. These four bevels 4|, 42, 43 and 44 are located on the flat portion of shaft 33 in the area engaged by spring clip 33.

The operation of this switching device will be best understood by a reference to Figs. 8 and 7. As shown in Fig. 6, switch blade 3 is positioned on the fixed contact corresponding with terminal l2, that is, in the number I position shown by Fig. 2. A movement of knob 3 to the left results in the switch blade being rotated counterclockwise to the off position; a rotation to the right of knob 3 rotates the switch blade in a clockwise direction to the second position. As shown in Fig. 6, no force is being applied tending to rotate the switch blades. Under this condition it will be seen that the spring clip 33 engages only the flat sides of shaft 33 and is not in contact with any of the beveled portions. Therefore, initially, when a force is applied tending to rotate shaft 33, the torque applied tending to rotate the switch blade 3 by the driving engagement with clip 33 is the force applied times the radius extending from the axis of shaft 33 to the point on the flat side where the bevel begins. As additional force is applied tending to rotate shaft 33 the torque gradually increases in approximately direct proportion to the increase in the force, since the radius through which the force is applied remains constant. Under these conditions switch blade 3 does not rotate since the restraining influence resulting from co-operation between dimple 33 and aperture 24 in the base prevents movement. However, as additional rotational force is applied to shaft 33, the engaging legs of clip 33 gradually spread permitting shaft 33 to rotate relative to clip 33 and switch blade 3.

Thus handle 3 is rotated through a predetermined angle, preferably slightly less than the angular spacing of adjacent fixed contact positions, without any corresponding movement of switch blade 3. When this predetermined angle is reached, however, clip 33 suddenly comes into engagement with bevels 42 and 43. This position of engagement is shown by Fig. 7 and it is apparent that the radius through which the torque is being applied is now increased to the distance from the axis of the shaft to the outermost corner. This sudden increase in the radius through which the force is applied results in a sudden increase in the torque tending to rotate switch blade 3 through the driving engagement with clip 33. The resulting sudden increase in the torque is sufficient to overcome the restraining influence caused by engagement of dimple 33 with aperture 24, and, therefore, switch blade 3 rotates clockwise one step to engage the next contact ll.

It is obvious that a similar action takes place with a rotation of shaft 33 in a counterclockwise direction, since bevels are provided on all four sides of the flat portion of shaft 33. While the co-operation between dimple 33 and the apertures in base I tend to provide a stepping action for switch blade 3, if bevels 4| through 44 were omitted, it would be necessary to achieve a very exact relationship between the driving torque developed by clip 33 and the restraining torque provided by engagement of dimple 33 with aperture 24, a condition practically impossible to maintain in mass production. My construction merely requires that the restraining torque should be somewhere between the driving torques developed before and after engagement of clip 33 with a pair of thebevels, so that switch blade 3 moves with 5 a snap action. This construction improves reliability and minimizes the chance of the switch blade assuming an intermediate position between two fixed contact positions.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited solely thereto since 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. A switching device comprising a base of insulation, a plurality of contact positions on said base, a switch blade rotatably attached to said base having one end sweeping said contact positions, means on said blade co-operating with means on said base restraining'the movement of said blade in steps corresponding with the spacing of said contact positions, a spring clip associated in driving relation with said blade, and a shaft engaged by said clip, the portion of said shaft engaged by said clip being flattened with bevels on each flat side extending to the outer edge thereof, said clip normally engaging said fiat sides, whereby upon application of a predetermined force to said handle said shaft rotates with respect to said clip resulting in engagement of diagonally opposite of said bevels with said clip to suddenly increase the torque tending to rotate said blade, the increased torque being suihcient to overcome said cooperating means to snap said blade from one contact position to an adjacent position.

2. In a snap-action switch having a rotary switch blade sweeping a plurality of fixed contact positions, means for suddenly increasing the torque causing rotation of said switch blade, said means comprising a resilient clip in driving relation with said switch blade, said clip having a pair of upstanding legs, an operating shaft including means to rotate said shaft, said shaft having fiat sides on one end thereof with bevels on each fiat side extending to the outer edge thereof, the flat end of said shaft extending between the legs of said clip, said legs normally engaging said fiat sides out of contact with said bevels, and upon application of a predetermined force to rotate said shaft, said shaft rotates with respect to said clip to bring said bevels in contact with said legs increasing the radius through which said force is applied to rotate said switch blade.

3. A switching device comprising a base of insulation, a plurality of contact positions on said base, a switch blade rotatably attached to said base having one end thereof sweeping said contact positions, means on said blade co-operating with means on said base tending to restrain movement of said blade in steps corresponding with 2,023,219

6 the spacing of said contact positions, a spring clip associated in driving relation with said blade, and a shaft rotatably supported with respect to said base, said shaft having an operating knob on one end thereof and flat sides on its opposite end with bevels on the edges of said fiat sides,

' said clip normally engaging said flat sides only when no rotational force is applied to said shaft, and upon application of a predetermined rotational force to said shaft said clip engages only said bevels, whereby the torque radius is increased to overcome said restraining means and cause said switch blade to snap to an adjacent contact position.

4. An electric switch comprising an insulating base, a plurality of contact positions on said base, a switch blade rotatably carried by said base and having one end thereof sweeping said contact positions, means for restraining movement of said switch blade in steps corresponding to the spacing of said contact positions, and driving means for rotating said switch blade, said driving means comprising a spring clip in driving relation with said switch blade and having a pair of upstanding legs, and a shaft with rotating means therefor, said shaft having a portion engageable between the upstanding legs of said clip and providing first and second bearing points between said clip and said shaft, said first bearing points having a shorter radius from said shaft axis than said second bearing points, whereby on initial rotation of said shaft only said first bearing points engage said clip and upon further rotation said shaft rotates with respect to said clip to engage only said second bearing points, said restraining means preventing movement of said switch blade until engagement of said second bearing points.

5. A rotary snap action switch comprising fixed contact elements, a movable contact element, means restraining movement of said movable contact element, and driving means for rotating said movable contact element, said driving means comprising a shaft, and means interconnecting said shaft and said movable contact element, said shaft providing two sets of bearing points for rotating said interconnecting means, said first set of bearing points being at a shorter radius from said shaft axis than said second set, whereby a given force provides sufiicient torque to overcome said restraining means only upon rotation of said shaft with respect to said interconnecting means to engage said second set of bearing points.

PHILIP HUTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date De Reamer Dec. 8, 1935 Number

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