US2943165A - Electric switch - Google Patents

Description

June 28, 1960 L. J. FICHTER ELECTRIC SWITCH Filed Oct. 10, 1958 PatentedJune 28,.19602 ELECTRIC SWITCH Ludwig J. Fichter, Chicago, Ill., assignor to Oak Mfg. (30., Chicago, Ill., a corporation of Illinois 'Filed Oct. 10, 1958, Ser. No. 766,610

2 Claims. (Cl. 200-67) I This invention relates to an electric switch and more particularly to a snap-acting switch having desirable operatingcharacteristics and sensitive to small mechanical forces for operating same.

In the operation of a snap action mechanism, it is necessary to store mechanical energy in a portion of the system prior tothe actual snapping of the movable member from one position to another. As a rule, during the storage of energy, the movable member is subject to creepagein preparation for the final snap action. Where snap action mechanism is used for operating electric switches, this creepage is responsible for undesirable contact action and frequently results in arcing at the contacts.

Various attempts have been made to overcome this creepage. tendency with indifferent success.

This invention provides a snap action mechanism wherein combined mechanical and magnetic forces are utilized for effecting snap action. By virtue of a lost motion coupling together with magnetic attraction the effects of creepage insofar as contact action is concerned is substantially eliminated.

In order that theinvention may be understood, it will now be disclosed in connection with the drawings wherein Figure 1 is a top view of a construction embodying the present invention.

Figure 2 is a side view of the construction illustrated in Figure 1, certain parts being in section.

Figure 3 is a section along line 33 of Figure 2.

Figure 4 is an end view from the actuating end of the switch.

Figure 5 is a section along line 5--5 of Figure 2.

The switch construction includes stack consisting of layers of insulation and conducting material rigidly clamped together by bolts 11 and 12. Stack 10 is generally similar to the stack in vibrators used in automobile radios and the like. Rigidly clamped in stack 10 are side plates and 15.

Each of plates 14 and 15 carries at the end thereof permanent magnets 16 and-17, respectively. The end of each plate 14 and 15 is bent to provide a generally U-shaped clamp having arms 18 and 19 and bight portion 20. Permanent magnet 16 in this instance is disposed between arms 18 and 19 and is firmly attached to bight 20 by suitable means.

As illustrated here, magnet 16 and bight 29 are provided with apertures through which rivet 22 extends. Rivet 22 may be magnetic or nonmagnetic although the latter is preferred. Permanent magnet 16 may also be soldered into position or otherwise firmly attached. The attachment should be firm enough so that the permanent magnet will remain in position in spite of the vibration to which the magnet may be subjected.

Permanent magnet 16 is generally U-shaped and has pole faces 24 and 25 spaced from each other and extending in a direction across the end of plate 14. It is clear that the magnetic circuit is independent of support ing plate 14 so that the latter may be of any material, Whether magnetic or not.

is similarly attached to platecorresponding pole pieces 24!;

Permanent magnet 17 15 and is provided with and 25.

Suitably supported instack 10 are stationary contact. supportarms 26 and 26. Each support arm hastermii nal portion 27 and 27 extending beyond the stack away, from the switch proper. Contact arm 26 carries atthet free end thereof stationary contact button 29. Similarly, contactarrnzfi carries stationary contact button 29'. These two stationary contact buttons are disposed opposite but spaced from each other. v

As is clear from the drawing, the permanentmagnets. are further from the stack thanthe stationary; contact buttons; Carried by stack 10 is movable contact arm 31; havingterminal portion 32 and carrying movable contact- 33. Movable contact 33 is double faced and extends om.- opposite-sides of spring arm 31. Springarm 21 may;- be of any suitable spring reed material, either magnetic;- or nonmagnetic. Arm 31 carries armature'34 suitably, attached thereto in position for cooperation with the, pole pieces of permanent magnets 16 and 17. As illustrated here, armature. 34 extends on opposite sides of the spring arm and may consist of two pieces of softiron. soldered or otherwise rigidly attached back toback to the spring arm.

Spring arm 31 has flexible tip portion 36 extending;- beyond armature 34. Tip portion 36 is substantially; more flexible than the body of spring arm 31 and this, may beachieved by narrowing the spring material, as; illustrated in Figure 3. v I

Rigidly supported-in stack 10 is flexible actuatingarm, 38 having the interior portion thereof cut out to provide; window 39 for clearingspning arm 31 and the permanent magnets. Actuating. arm 38 is a spring reed and extends; away from the stack beyond tip 36 and has free end p0r-.- tion 40 to which is rigidly attached plates 41 and 42-011; opposite sides thereof. Plates 41-and 42 have end portions 43 and 44bent away from each other and are so located asv to limit the travel of tip portion 36 of the? spring contact arm.

End portion 40 of actuating arm 38 may have any suit!- able means attached thereto or cooperating therewithfor; actuating the same. As illustrated, end portion 40;-carries roller '46 suitably supported between arms 47 and 48 carried by plate 42. However, this is exemplary andi instead of a roller, a pin or other means for moving end; portion 40. of the actuating arm may. be -provided. 'As shown in dotted-lines in Figure 2, the movement of end: portion 44) of actuating arm 38 shouldbe transversely of. the arm.. I

Figure 2 shows in full lines the normal position of the movable contact arm with armature 34 against-bottom. magnet 17; From this position, an upward force upon portion 40 of the actuating arm will cause diverging portion 44 to engage tip 36 of the movable contact arm and start to bend the tip upwardly. Since the permanent magnet and armature is between tip 36 of the arm and cooperating contacts 33 and 29', it will be clear that no contact creepage can occur. As the upward force on tip portion 40 increases, the attraction of the magnet for the armature is overcome and the spring contact arm suddenly moves away to open contacts 33 and 29'.

The movement of contact arm 31 away from permanent magnet 17 results in armature 34 going toward magnet 16 and reaching the same. The parts are so proportioned that movable contact 33 will firmly engage the cooperating stationary contact when armature 34 engagw the cooperating permanent magnet pole faces.

Due to the divergence of portions 43 and 44, a lost motion connection for spring tip portion 36 is provided. The lost motion permits tip portion 36 to bend as actuating portion 40 moves up and after the armature is free 3 from bottom magnet 17, the lost motion permits the armature to snap into engagement with top magnet 16. The action is similar when the Spring arm is moved downwardly from the dottedline position illustrated in Figure 2 In both casesalsnap opening and closing of the'contacts is assured. 7

It is clear that one of the two stationary contacts 29 or 29 may be omitted. It is also clear that a number of contacts may be disposed in tandem so that a number of movable contacts may close against a number of stationary contacts. Such an arrangement is similar to the self-rectifying type of vibrator wherein two movable contacts operate between two pairs of stationary contacts.

In all cases where movable contact 33 closes against a stationary contact, as for example, contact 29, it is necessary to have a permanent magnet, such as 16, for cooperation to effect good contact action. Thus magnet 16 and contact 29 may constitute one pair of elements for insuring a snap-acting opening and closing of these two contacts. In such case it is possible toomit stationary contact 29' and itssupporting arm and it would be possible to omit bottom magnet 17 and supporting plate 15. However, some means to limit the downward movement of tip portion 40 of actuating arm 38 should be provided to avoid extreme movement of the spring arm. Such a construction would provide a simple snap-acting switch having one movable and one stationary contact.

Instead of having permanent magnets 16 and 17 on opposite sides of armature 34 for alternate cooperation therewith, it is possible to reverse the construction and have 16 and 17 as armatures and 34 as a permanent ma net. It is also possible to have 34 as a permanent magnet and retain magnets 16 or 17 or both in which case care should be taken to insure that part 34 is properly magnetized and has the proper polarity. In fact, part 34 would be modified so that each side would have a U- shaped face similar to the U-shaped faces of magnets 16 and 17. It is also possible to have different arrangements of pole faces in case member 34 is to be permanently magnetized.

' The arrangement illustrated, however, is satisfactory since a relatively strong permanent magnet may be used at the end of stationary arms 14 or 15 or both with a relatively light armature 34 carried by spring arm 31. Such an arrangement will permit of high speed operation. If spring arm 31 is of soft spring steel then a separate armature may be unnecessary. However, armature 34 is desirable since the faces thereof may be properly disposed to engage the magnet pole faces without excessive travel of the spring arm.

Instead of having spring tip portion 36 freely movable between diverging portions 43 and 44, it is possible to rigidly attach the end of the contact arm to portion 40 of the actuating arm. In such case, tip portion 36 should be made long enough and flexible enough so that in effect substantial fiexure of portion 36 between armature 34,

.4 and its bound end will be permitted. This would necessitate a substantially longer actuating arm 38 extending for a substantial distance beyond the permanent magnets. However, the arrangement illustrated wherein tip portion 36 is free from the actuating arm is simple and highly effective. The surface of the diverging arm contacted by spring tip portion 36 permits sliding of the tip as the actuating arm moves.

It is also possible to have tip portion 36 quite stiff and dispose coil springs on opposite sides of tip 36, such coil springs extending to plate extensions of 43 and 44. Such plate extensions 43 and 44 would form the sides of a U so that in effect, tip 36'would operate between the arms of a U against coil springs.

Instead of electrical contacts, reed 31 could operate other means.

What is claimed is:

1. A snap action electric switch comprising a stack carrying a pair of rigid flat arms in spaced parallel relation, a permanent magnet at each end of said rigid arms, said two permanent magnets being spaced from each other and having their pole faces disposed opposite each other, a reed having one end carried by said stack disposed between said rigid arms and extending past said permanent magnets, an armature carried by said reed for alternate cooperation with each permanent magnet, said reed being adapted to be flexed so that said armature engages one or the other permanent magnet, a spring actuating arm having one end carried by said stack and extending beyond the free ends of said rigid arms to provide a free movable actuating end portion, said spring arm being normally flat and having a window cut out therefrom so that said reed may move through the window, said reed having a generally flat end portion of increased flexibility extending beyond the armature and toward the free end of the actuating arm, said actuating arm having means for engaging the end of the reed so that said end of the reed must move with the free end of the actuating arm, said engagement of the actuating arm end portion and reed end portion permitting said reed to be flexed by movement of the actuating arm, a movable electric contact carried by said reed at a region between the armature and stack and at least one stationary contact for cooperation with said movable contact. r

2. The construction according to claim 1 wherein said engaging means for the end of the reed comprises two diverging parts on the actuating arm to provide a V into which the free end of the reed can fit.

References Cited in the file of this patent UNITED STATES PATENTS 2,493,294 Kronmiller Jan. 3, 1950 2,500,476 Von Stoeser Mar. 14, 1950 2,518,480 Lilia Aug. 15, 1950 2,782,278 Peters Feb. 19, 1957

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