US2508381A - Snap acting contactor - Google Patents

Description

May 23, 1950 P. e. FRERER I SNAP ACTING CONTACTOR Filed April 1, 1946 I5 70 20 23 32 54 35 I0 40 .32 4a 2a 30 Z4- 27 25' 2s 3 PAUL 'G. FEE/PEI? FIG. 5

rttentedmi 23, 1950' slur some CONTACTOB Paul G. Fret-er, Baltimore, Md., asslgnor to Bendlx Aviation Corporation, Baltimore, Md., a

corporation of Delaware Application April 1, 1946, Serial No. 658,602

9 Claims. 1

This invention relates to snap acting mechanisms and more particularly to a snap acting mechanism especially adapted for use in electric switches.

In performing control operations, there are many applications for an electric switch of unitary structure in which the displacement of an actuator member causes the opening or closing of an electric circuit. If such a device is to function satisfactorily and deliver long reliable service in the many environments in which it may find employment, it has been found that certain fundamental principles relating to switching operations must be observed:

1. The operation of the contacts must take place swiftly and with a motion substantially independent of the mannerin which the actuator causing the opening or closing of the switch is moved by its associated driving member.

2. The contacts must remain firmly engaged up to the time of their separation, which is to say that the time during which the contact pressure is sensibly zero must be reduced to a minimum.

3. Upon engagement of the contacts subsequent separation or bouncing thereof should be prevented as these multiple interruptions of the circuit greatly increase the rate of contact deterioration.

Many methods have been employed for pro= ducing the unstable force vs. contact deflection characteristic required for snap action among which the magnetic snap action and the over center snap action are representative. The switch illustrated and discussed herein employs the magneticmethod of securing the snap action but it is to be recognized that this characteristic may be imparted by means of any other expedient adapted to the purpose, many of which are currently well known.

In addition to these practical operating requirements, it is also desirable from other practical standpoints that it be possible to assemble the switch and adjust it with all the parts freely accessible and occupying the same relative positions as in the assembly when finally mounted in its operating environment, while yet providing tude of a flexible contact carrying blade is restricted.

It is another object of the invention to provide a snap acting mechanism driven-through a resilient link in which provision is made for operation of the element independently of the snap action characteristic when the deflection of the resilient element exceeds a predetermined value.

It is a further object of the invention to provide new and novel snap acting electric switching means with a reduced number of parts and improved operating characteristics.

Yet another object of the invention is to provide new and novel snap action switching means having a removable cover and an external actuator in which the operating characteristics are substantially unaltered by the presence or absence of the cover. a

Still a. further object of the invention is to provide snap acting electric switching means in which the contact pressure exceeds a predetermined until the moment of contact separation.

Other objects and advantages of the invention will in part be obvious and in part be disclosed when the following specification is read in conjunction with the drawings in which:

Figure l is a plan view of a switch embodying the principles of the invention with the cover removed.

Figure 2 is a view in elevation'of the switch with the cover removed and situated directly there above.

electric switches in which the oscillation amplil Figure 3 is an end view of the same switch and cover viewed from the operating blade support end.

Figure 4 is an end view of the said switch from the magnet end with the mounted position of the cover showing in dashed lines.

Figure 5 is a bottom view illustrating the terminal connections to the switch.

Referring now to Figure 1 of the drawings, the switch is assembled on a base It), which may be fabricated of any suitable insulating material such as the currently popular phenol-formaldehyde condensation products. The base It] is roughly rectangular in form and traversed at diagonally spaced comers by a pair of mounting apertures l2. The ends of the base are recessed at H to accommodate the mounting ears of an associated cover [6 shown in the upper portions of Figures 2 and 3. The embossed or raised areas ll of the base It define a locating border assisting in the placement of the cover It during assembly and assist in the exclusion oi moisture and dirt.

Along one of the longer edges of the base Hi there is located the actuator support projection 2| pierced by an aperture 23 receiving the actuator 46. Projection 2| is divided into two portions, one having a relatively small dimension, indicated at 25, and the other, 21, somewhat larger, forming a flange-like backing cooperating with the interior of the cover l6 to seal ofi the entrance against moisture and dirt.

Within the border I8, a bracket plate 20 is secured by rolling over the inner end of a contact stud 22 molded in place. The bracket arm 24 projects perpendicularly from the bracket plate 20 and is tapped and threaded to accommodate the clamping screws 26 which, with a bridging link 20, secure one end of a resilient operating blade 30 to the bracket arm 24. The operating blade 30 extends along and substantially parallel to the base l and has secured thereto, at a point somewhat'removed from the point of attachment to the bracket arm 24, a relatively rigid armature member 32. The armature member 32 may be secured by rivets in the manner illustrated or by other expedient means and is of para-magnetic material, while the operating blade 30 is substantially non-magnetic.

As shown, the armature 32 is offset from and extends parallel to but spaced from, the operating blade 30 by a small but appreciable distance. The free end of the operating blade 30 may have a U shape opening as indicated at 34 through which there passes an adjusting screw 36 threaded into the armature 32. The opening 34 in the operating blade 30 clears the shank of the adjusting screw 36 but not the head thereof, thereby determining the travel of the operating blade 30 with respect to armature 32 in this sense or direction. The operating blade 36 also carries a contact 38, secured by spinning or rolling over the rearward portion thereof. Adjusting screw til is threaded into the armature 32 immediately to the rear of the mounting for contact 33 and rotation of the screw 40 hence affords a means for controlling the minimum clearance between the operating blade 30 and the armature 32; thus the adjusting screws 36 and 40 serve to individually determine the limits of travel of the operating blade 30 with respect to the armature 32 in either direction. An operating arm 42 is struck out of the central portion of the operating blade 3!) and extends angularly therefrom, its dimpled end 44 terminating opposite the rear surface of the actuator 46 passing through the aperture 23 in the projection 2|.

A second bracket plate 48 is secured to the right hand portion of the mounting area defined by the mounting border l8 and carries the magnet supporting arm 50 and the split contact'support 52. A magnet 54 is anchored to the upwardly extended arm 50 by the clamping plate 56 and associated mounting screw 58. The horseshoe ends of magnet 54 are most readily seen in Figure 4. The free poles of the magnet 54 are adjacent to magnetic armature 32 and exert a biasing force thereon. The split bracket 52 is tapped to receive the screw 60 tipped by contact 62 and it is at once obvious that the biasing force exerted by magnet 54 on armature 32 tends to urge contact 38 into engagement with contact 62. Hence, in the arrangement shown, the contacts are normally closed. The diiierent-ial of switch operation is controlled by movement of the contact 62 toward or away from the operating blade 30 by rotation of the screw 60. The differential decreases as 4 the contact 62 is moved toward the operating blade 30, and increases when the contact 62 is moved in the reverse direction. The split bracket 52 resiliently clamps the screw 60 to prevent disturbance of the adjustment in the presence of vibration and the like.

Electrical connection to the switch contacts is established by attachment of the leads to the contact studs 22 using the screws I9 extending into the central threaded portion of the appertures of said studs 22, as seen in Figure 5.

Inward travel of the actuator 46 deflects the operating arm 42, the armature 32 remaining in position until the force builds up sufficiently to overcome the magnetic attraction between armature 32 and magnet 54, at which time the armature 32 moves swiftly away from the magnet 55. During contact closure the operating blade 30 is pressed back toward the armature 32 to the extent' permitted by the adjustment of the press back adjusting screw 40 limiting travel in this sense. Due to this press back the head of the bias adjusting screw 36 normally clears the surface of the operating blade 30. Because of the inertia of the contact 38 and the initial bias in the operating blade 30, contacts 38 and 62 remain relatively firmly engaged during the initial movement of the armature 32. After the armature 32 has traveled somewhat and thereby attained appreciable velocity, the under surfaces of the head of the screw 36 engage the operating blade 30, forcibly and rapidly separating the contacts in a minimum period of time with a minimum amount of are.

It may happen that because of contact welding or other unpredictable causes, the stress built up in operating arm 42 is not sufficient to initiate the movement of the armature 32 out of the field of the magnet 54. When used in some installations or classes of apparatus, the consequence of failure to operate may prove disastrous and to avoid this a third screw which may be identified as the over travel disengagement adjusting screw 63 is threaded into the armature 32 directly to the rear of the actuator 46. Travel of the actuator 46 beyond a predetermined point determined by the adjustment of screw 54 effects a solid engagement directly transmitting separating force to the armature 32 independently of any intermediate resilient linkage to separate the contacts and prevent damage to the apparatus.

As the actuator 46 gradually moves outwardly in a sense releasing the stress in the operating arm 42, a point is finally reached where the tractive effort exerted by the magnet 54 on the armature 32 overcomes the tension of the lever 30 resisting such movement, after which the armature 32 moves quickly to a position adjacent the magnet 54. As the armature moves toward the magnet, the contact 38 comes into engagement with the contact 62 and the operating blade 30 approaches the armature 32, clearing the bias adjusting screw 36. Because of the initial bias impressed upon the operating blade 30 by screw 36 there is, from the moment of engagement, a continuous contact pressure preventing subsequent bouncing or separation of the contacts. In the space of a few micro-seconds the armature 32 has continued its travel bringing the press back adjusting screw 40 into forcible abutment with the rear of contact 38 whereby the full force developed by the magnet is directly brought to bear upon the contacts without the interposition of any intermediate resilient linkage. In addition, after the establishment of this abutting relation essential characteristics thereof.

the armature 82 affords a current path shunting that through operating blade It thus reducin the heat developed within the switch housing.

In a particular combination, the switch was found to operate with a minimum of differential and with the best contact make and break characteristic when the screw 38 was adjusted to place a stress of the order of 2 grams on the operating blade 30 measured at the contact 38, and the screw 40 was adjusted so that a force at contact 38 of the order of 6 grams was required to drive the rear of contact 38 into abutment with the end of screw 40. The most favorable ratio for these two values of stress has been found to lie between 2:1 and 5:1 if bounce is to be avoided and a minimum differential attained in operating characteristic. i A

The cover I6 is provided with apertures 6 which are in register with the apertures l2 when the cover is in position, affording a means for mounting the'switch with either the cover or the base toward the mounting surface. Alternative provision for mounting is afforded by apertures. l5 extending through and transversely of the longitudinal axis of the base III as appears from Figures 2 and 3. In addition tothe apertures 6B anopening 68 is provided in one of the lateral surfaces of the cover It of a size adapted to fit over the reduced portion 25 of projection 2| and cooperate with the flange constituted by the larger portion 21 of the projection 2| to provide a dust tight seal.

It is obvious from the foregoing that the relationship of the actuator to the switch structure is determined solely by the relative position of the parts on the base and that this relation is in no way affected by the presence or removal of the cover It; hence, the switch may be calibrated and tested with the cover removed and the cover added as the final step in the assembly operation.

While the switch described is one in which the contacts are normally closed it is quite clear that the principles of the invention may be applied with equal advantage to any form of switch whether of the single or multiple contact or of the normally open type. It is further obvious that although a magnet has been shown as the means for providing the bias force essential to snap action operation, any mechanical linkage system having a suitable force vx. deflection characteristic may be employed as well.

The invention may be embodied in other specific forms without departing from the spirit or The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced thereby.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a snap acting mechanism, a base, a sup,- port secured to said base, a flexible member carried by said support, a first electrical contact carried by said flexible member, a relatively rigid member secured to said flexible member and acted upon in a first sense by a biasing force, said relatively rigid member being moveable relative to said flexible member, a resilient member cou-' pled with said second member and extending intermediately thereof, adjustable means for limiting the relative movement between said flexible member and said rigid member in a first sense.

adjustable means for limiting-the relative movement between said flexible member and said rigid member in a second sense, means secured to said base for limiting the excursion. of said flexible member in said first sense, said means comprising a second electrical contact cooperating with said first electrical contact and adjustable thereto and actuating means engageable with said resilient member.

2. In a, snap acting mechanism, a base having an apertured extension extending substantially perpendicular to a mechanism supporting surface on said base, a support secured to said supporting surface, a flexible member carried by said support, first electrical contact carried by said flexible member, a relatively rigid member secured to said flexible member and acted upon in a first sense by a biasing force, said relatively rigid member being moveable relative to said flexible member, a resilient member coupled with said second member and extending intermediately thereof, adjustable means for limiting the relative movement between said flexible member and said rigid member in a first sense, adjustable means for limiting the relative movement between said flexible member and said rigid member in a second sense,

, means secured to said base for limiting the excursion of said flexible member in said first sense, said means comprising a second electrical contact cooperating with said first electrical contact and adjustable thereto, and actuating means supported by said apertured extension engageable with said resilient member.

3. In electrical switching apparatus, a base, electrically conductive means extending through said base at one end and securing thereto an operating blade support, electrically conductive means extending through said base at the other end thereof and securing thereto a magnet and an adjustable contact, anoperating blade carried by said operating blade support, a contact mounted on said operating blade and engageable with said adjustable contact, an armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said. magnet, means carried by said armature for adjustingthe maximum clearance between said operating blade and said armature, means carried by said armature for adjusting the minimum clearance between said operating blade and said armature, a resilient arm extending laterally of said operating blade, means carried by said armature for adjusting the minimum clearance between said resilient arm and said armature, and an actuating member engageable with said resilient arm.

4. In electric switching apparatus, a base, electrically conductive means extending through said 1 base at one end and securing thereto an operating blade support, electrically conductive means extending through said base at the other end thereof and securing thereto a. magnet and an adjustable contact, an operating blade carried by said operating blade support, a contact mounted on said operating blade and engageable with said adjustable contact, an armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said magnet, means for adjusting the maximum clearance between said operating blade and said armature, means for adjusting the minimum clearance between said operating blade 18 and said armature, a resilient arm extending lataccuser 7 erally of said operating blade, means for adjusting the minimum clearance between said resilient arm and said armature, and switch operating means engageable with said resilient arm.

5. In electric switching apparatus, a base, electrically conductive means extending through said base at one end and securing thereto an operating blade support, electrically conductive means extending through said base at the other end thereof and securing thereto a magnet and an adjustable contact, an operating blade carried by said operating blade support, a contact mounted on said operating blade and engageable with said adjustable contact, an armature attached at one end to said operating blade and extending substantially rparallel thereto with the free end of said armature adapted to move in proximity to said magnet, means carried by said armature for adjusting the maximum clearance between said operating blade and said armature, means carried by said armature in register with said operating blade contact for adjusting the minimum clearance between said operating blade and said armature, a resilient arm extending laterally of said operating blade, an actuating member engageable with said resilient arm, and means carried by said armature in register with said actuating member for adjusting the minimum clearance between said resilient arm and said armature.

6. In electric switching apparatus, a base, electrically conductive means extending through said base at one end and securing thereto an operating blade support, electrically conductive means extending through said base at the other end thereof and securing thereto a magnet and an adjustable contact, an operating blade carried by said operating blade support, a contact mounted on said operating blade and engageable with said adjustable contact, an armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said magnet, means for determining the maximum clearance between said armature and said operating blade, an actuator, a resilient transmission link between said actuator and said armature, and means for adjusting the minimum clearance between said actuator and said armature.

7. In electric switching apparatus, a base, electrically conductive means extending through said base at one end and securing thereto an operating blade support, electrically conducting means extending through said base at the other end thereof and securing thereto a ma net and an adjustable contact, a relatively flexible operating blade attached at one end to said operating blade support and provided with an aperture at the free end thereof, a contact mounted on said operating blade and engageable with said adjustable contact, a relatively rigid armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said magnet, means carried by said armature projecting through said aperture at the free end of said operating blade for determining the maximum clearance between said armature and said operating blade, an actuator, a resilient trans 8 mission link between said actuator and said armature, and means for adjusting the minimum clearance between said actuator and said armature. i I I iawafl 8. In electric switching apparatus, a base, electrically conductive means extending through said base at one end and securing thereto an operating blade support, an operating blade relatively flexible in a predetermined fiexure plane attached at one end to said operating blade support, electrically conductive means extending through said base at the other end thereof and securing thereto a magnet and a contact mount, a contact carried by said contact mount and adjustable in said iiexure plane, a contact mounted on said operating blade and engageable with said adjustable contact, a relatively rigid armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said magnet, means for determining the maximum clearance between said armature and said operating blade, an actuator carried by said base and moveable parallel to said flexureplane, a re silient transmission link between said actuator and said armature, and means for adjusting the minimum clearance between said actuator and said armature.

9. In electric switching apparatus, a base, an operating blade support secured at one end of said base, an operating blade relatively flexible in a predetermined flexure plane attached at one end to said operating blade support, a magnet carried by said base adjacent the other end of said base,

a contact carried by said base situated intermediate said magnet and said operating blade support adjustable along a line parallel to said flexure plane, a contact mounted on said operating blade and engageable with said adjustable contact, a relatively rigid armature attached at one end to said operating blade and extending substantially parallel thereto with the free end of said armature adapted to move in proximity to said magnet, means for determining the maximum clearance between said armature and said operating blade, an actuator carried at one side of and centrally of said base moveable parallel to said flexure plane, a, resilient transmission link between said actuator and said armature, and means for adjusting the mininum clearance between said actuator and said armature.

PAUL G. FRERER.

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

UNITED STATES PATENTS Number Name Date 1,869,646 Anderson Aug. 2, 1932 2,121,079 Eskin June 21, 1938 2,232,248 Judson Feb. 18, 1941 2,265,486 Judson Dec. 9, 1941 2,273,671 Ullberg Feb. 17, 1942 2,337,001 Ray Dec. 14, 1943 2,368,679 Popp Feb. 6, 1945 2,385,887 Shaw Oct. 2, 1945 2,410,055 Frerer Oct. 29, 1946

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